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1
2118-2121
e , sin–1 x ≠ , 2 2 −π π , i e , x ≠ – 1, 1, i
1
2119-2122
, sin–1 x ≠ , 2 2 −π π , i e , x ≠ – 1, 1, i e
1
2120-2123
e , x ≠ – 1, 1, i e , x ∈ (– 1, 1)
1
2121-2124
, x ≠ – 1, 1, i e , x ∈ (– 1, 1) To make this result a bit more attractive, we carry out the following manipulation
1
2122-2125
e , x ∈ (– 1, 1) To make this result a bit more attractive, we carry out the following manipulation Recall that for x ∈ (– 1, 1), sin (sin–1 x) = x and hence cos2 y = 1 – (sin y)2 = 1 – (sin (sin–1 x))2 = 1 – x2 Also, since y ∈ , 2 2 π π   −   , cos y is positive and hence cos y = 2 1 x − Thus, for x ∈ (– 1, 1), 2 1 1 cos 1 dy dx y x = = − 2 1 1 x − 2 1 1 x − − 2 1 1 x + f(x) sin–1 x cos-1 x tan-1x Domain off (-1, 1) (-1, 1) R f 1(x) Rationalised 2023-24 CONTINUITY AND DIFFERENTIABILITY 125 EXERCISE 5
1
2123-2126
, x ∈ (– 1, 1) To make this result a bit more attractive, we carry out the following manipulation Recall that for x ∈ (– 1, 1), sin (sin–1 x) = x and hence cos2 y = 1 – (sin y)2 = 1 – (sin (sin–1 x))2 = 1 – x2 Also, since y ∈ , 2 2 π π   −   , cos y is positive and hence cos y = 2 1 x − Thus, for x ∈ (– 1, 1), 2 1 1 cos 1 dy dx y x = = − 2 1 1 x − 2 1 1 x − − 2 1 1 x + f(x) sin–1 x cos-1 x tan-1x Domain off (-1, 1) (-1, 1) R f 1(x) Rationalised 2023-24 CONTINUITY AND DIFFERENTIABILITY 125 EXERCISE 5 3 Find dy dx in the following: 1
1
2124-2127
To make this result a bit more attractive, we carry out the following manipulation Recall that for x ∈ (– 1, 1), sin (sin–1 x) = x and hence cos2 y = 1 – (sin y)2 = 1 – (sin (sin–1 x))2 = 1 – x2 Also, since y ∈ , 2 2 π π   −   , cos y is positive and hence cos y = 2 1 x − Thus, for x ∈ (– 1, 1), 2 1 1 cos 1 dy dx y x = = − 2 1 1 x − 2 1 1 x − − 2 1 1 x + f(x) sin–1 x cos-1 x tan-1x Domain off (-1, 1) (-1, 1) R f 1(x) Rationalised 2023-24 CONTINUITY AND DIFFERENTIABILITY 125 EXERCISE 5 3 Find dy dx in the following: 1 2x + 3y = sin x 2
1
2125-2128
Recall that for x ∈ (– 1, 1), sin (sin–1 x) = x and hence cos2 y = 1 – (sin y)2 = 1 – (sin (sin–1 x))2 = 1 – x2 Also, since y ∈ , 2 2 π π   −   , cos y is positive and hence cos y = 2 1 x − Thus, for x ∈ (– 1, 1), 2 1 1 cos 1 dy dx y x = = − 2 1 1 x − 2 1 1 x − − 2 1 1 x + f(x) sin–1 x cos-1 x tan-1x Domain off (-1, 1) (-1, 1) R f 1(x) Rationalised 2023-24 CONTINUITY AND DIFFERENTIABILITY 125 EXERCISE 5 3 Find dy dx in the following: 1 2x + 3y = sin x 2 2x + 3y = sin y 3
1
2126-2129
3 Find dy dx in the following: 1 2x + 3y = sin x 2 2x + 3y = sin y 3 ax + by2 = cos y 4
1
2127-2130
2x + 3y = sin x 2 2x + 3y = sin y 3 ax + by2 = cos y 4 xy + y2 = tan x + y 5
1
2128-2131
2x + 3y = sin y 3 ax + by2 = cos y 4 xy + y2 = tan x + y 5 x2 + xy + y2 = 100 6
1
2129-2132
ax + by2 = cos y 4 xy + y2 = tan x + y 5 x2 + xy + y2 = 100 6 x3 + x2y + xy2 + y3 = 81 7
1
2130-2133
xy + y2 = tan x + y 5 x2 + xy + y2 = 100 6 x3 + x2y + xy2 + y3 = 81 7 sin2 y + cos xy = κ 8
1
2131-2134
x2 + xy + y2 = 100 6 x3 + x2y + xy2 + y3 = 81 7 sin2 y + cos xy = κ 8 sin2 x + cos2 y = 1 9
1
2132-2135
x3 + x2y + xy2 + y3 = 81 7 sin2 y + cos xy = κ 8 sin2 x + cos2 y = 1 9 y = sin–1 2 2 1 x x     +  10
1
2133-2136
sin2 y + cos xy = κ 8 sin2 x + cos2 y = 1 9 y = sin–1 2 2 1 x x     +  10 y = tan–1 3 2 3 , 1 3 x x x   −   −  1 1 3 3 x − < < 11
1
2134-2137
sin2 x + cos2 y = 1 9 y = sin–1 2 2 1 x x     +  10 y = tan–1 3 2 3 , 1 3 x x x   −   −  1 1 3 3 x − < < 11 2 1 2 1 , cos 0 1 1 x y x x −   − = < <   +  12
1
2135-2138
y = sin–1 2 2 1 x x     +  10 y = tan–1 3 2 3 , 1 3 x x x   −   −  1 1 3 3 x − < < 11 2 1 2 1 , cos 0 1 1 x y x x −   − = < <   +  12 2 1 2 1 , sin 0 1 1 x y x x −   − = < <   +  13
1
2136-2139
y = tan–1 3 2 3 , 1 3 x x x   −   −  1 1 3 3 x − < < 11 2 1 2 1 , cos 0 1 1 x y x x −   − = < <   +  12 2 1 2 1 , sin 0 1 1 x y x x −   − = < <   +  13 1 22 , cos 1 1 1 x y x x −   = − < <   +  14
1
2137-2140
2 1 2 1 , cos 0 1 1 x y x x −   − = < <   +  12 2 1 2 1 , sin 0 1 1 x y x x −   − = < <   +  13 1 22 , cos 1 1 1 x y x x −   = − < <   +  14 ( ) 1 2 1 1 , sin 2 1 2 2 y x x x − = − − < < 15
1
2138-2141
2 1 2 1 , sin 0 1 1 x y x x −   − = < <   +  13 1 22 , cos 1 1 1 x y x x −   = − < <   +  14 ( ) 1 2 1 1 , sin 2 1 2 2 y x x x − = − − < < 15 1 12 1 , sec 0 2 1 2 y x x −   = < <  −   5
1
2139-2142
1 22 , cos 1 1 1 x y x x −   = − < <   +  14 ( ) 1 2 1 1 , sin 2 1 2 2 y x x x − = − − < < 15 1 12 1 , sec 0 2 1 2 y x x −   = < <  −   5 4 Exponential and Logarithmic Functions Till now we have learnt some aspects of different classes of functions like polynomial functions, rational functions and trigonometric functions
1
2140-2143
( ) 1 2 1 1 , sin 2 1 2 2 y x x x − = − − < < 15 1 12 1 , sec 0 2 1 2 y x x −   = < <  −   5 4 Exponential and Logarithmic Functions Till now we have learnt some aspects of different classes of functions like polynomial functions, rational functions and trigonometric functions In this section, we shall learn about a new class of (related) functions called exponential functions and logarithmic functions
1
2141-2144
1 12 1 , sec 0 2 1 2 y x x −   = < <  −   5 4 Exponential and Logarithmic Functions Till now we have learnt some aspects of different classes of functions like polynomial functions, rational functions and trigonometric functions In this section, we shall learn about a new class of (related) functions called exponential functions and logarithmic functions It needs to be emphasized that many statements made in this section are motivational and precise proofs of these are well beyond the scope of this text
1
2142-2145
4 Exponential and Logarithmic Functions Till now we have learnt some aspects of different classes of functions like polynomial functions, rational functions and trigonometric functions In this section, we shall learn about a new class of (related) functions called exponential functions and logarithmic functions It needs to be emphasized that many statements made in this section are motivational and precise proofs of these are well beyond the scope of this text The Fig 5
1
2143-2146
In this section, we shall learn about a new class of (related) functions called exponential functions and logarithmic functions It needs to be emphasized that many statements made in this section are motivational and precise proofs of these are well beyond the scope of this text The Fig 5 9 gives a sketch of y = f1(x) = x, y = f2(x) = x2, y = f3(x) = x3 and y = f4(x) = x4
1
2144-2147
It needs to be emphasized that many statements made in this section are motivational and precise proofs of these are well beyond the scope of this text The Fig 5 9 gives a sketch of y = f1(x) = x, y = f2(x) = x2, y = f3(x) = x3 and y = f4(x) = x4 Observe that the curves get steeper as the power of x increases
1
2145-2148
The Fig 5 9 gives a sketch of y = f1(x) = x, y = f2(x) = x2, y = f3(x) = x3 and y = f4(x) = x4 Observe that the curves get steeper as the power of x increases Steeper the curve, faster is the rate of growth
1
2146-2149
9 gives a sketch of y = f1(x) = x, y = f2(x) = x2, y = f3(x) = x3 and y = f4(x) = x4 Observe that the curves get steeper as the power of x increases Steeper the curve, faster is the rate of growth What this means is that for a fixed increment in the value of x (> 1), the increment in the value of y = fn (x) increases as n increases for n = 1, 2, 3, 4
1
2147-2150
Observe that the curves get steeper as the power of x increases Steeper the curve, faster is the rate of growth What this means is that for a fixed increment in the value of x (> 1), the increment in the value of y = fn (x) increases as n increases for n = 1, 2, 3, 4 It is conceivable that such a statement is true for all positive values of n, Rationalised 2023-24 MATHEMATICS 126 where fn (x) = xn
1
2148-2151
Steeper the curve, faster is the rate of growth What this means is that for a fixed increment in the value of x (> 1), the increment in the value of y = fn (x) increases as n increases for n = 1, 2, 3, 4 It is conceivable that such a statement is true for all positive values of n, Rationalised 2023-24 MATHEMATICS 126 where fn (x) = xn Essentially, this means that the graph of y = fn (x) leans more towards the y-axis as n increases
1
2149-2152
What this means is that for a fixed increment in the value of x (> 1), the increment in the value of y = fn (x) increases as n increases for n = 1, 2, 3, 4 It is conceivable that such a statement is true for all positive values of n, Rationalised 2023-24 MATHEMATICS 126 where fn (x) = xn Essentially, this means that the graph of y = fn (x) leans more towards the y-axis as n increases For example, consider f10(x) = x10 and f15(x) = x15
1
2150-2153
It is conceivable that such a statement is true for all positive values of n, Rationalised 2023-24 MATHEMATICS 126 where fn (x) = xn Essentially, this means that the graph of y = fn (x) leans more towards the y-axis as n increases For example, consider f10(x) = x10 and f15(x) = x15 If x increases from 1 to 2, f10 increases from 1 to 210 whereas f15 increases from 1 to 215
1
2151-2154
Essentially, this means that the graph of y = fn (x) leans more towards the y-axis as n increases For example, consider f10(x) = x10 and f15(x) = x15 If x increases from 1 to 2, f10 increases from 1 to 210 whereas f15 increases from 1 to 215 Thus, for the same increment in x, f15 grow faster than f10
1
2152-2155
For example, consider f10(x) = x10 and f15(x) = x15 If x increases from 1 to 2, f10 increases from 1 to 210 whereas f15 increases from 1 to 215 Thus, for the same increment in x, f15 grow faster than f10 Upshot of the above discussion is that the growth of polynomial functions is dependent on the degree of the polynomial function – higher the degree, greater is the growth
1
2153-2156
If x increases from 1 to 2, f10 increases from 1 to 210 whereas f15 increases from 1 to 215 Thus, for the same increment in x, f15 grow faster than f10 Upshot of the above discussion is that the growth of polynomial functions is dependent on the degree of the polynomial function – higher the degree, greater is the growth The next natural question is: Is there a function which grows faster than any polynomial function
1
2154-2157
Thus, for the same increment in x, f15 grow faster than f10 Upshot of the above discussion is that the growth of polynomial functions is dependent on the degree of the polynomial function – higher the degree, greater is the growth The next natural question is: Is there a function which grows faster than any polynomial function The answer is in affirmative and an example of such a function is y = f(x) = 10x
1
2155-2158
Upshot of the above discussion is that the growth of polynomial functions is dependent on the degree of the polynomial function – higher the degree, greater is the growth The next natural question is: Is there a function which grows faster than any polynomial function The answer is in affirmative and an example of such a function is y = f(x) = 10x Our claim is that this function f grows faster than fn (x) = xn for any positive integer n
1
2156-2159
The next natural question is: Is there a function which grows faster than any polynomial function The answer is in affirmative and an example of such a function is y = f(x) = 10x Our claim is that this function f grows faster than fn (x) = xn for any positive integer n For example, we can prove that 10x grows faster than f100 (x) = x100
1
2157-2160
The answer is in affirmative and an example of such a function is y = f(x) = 10x Our claim is that this function f grows faster than fn (x) = xn for any positive integer n For example, we can prove that 10x grows faster than f100 (x) = x100 For large values of x like x = 103, note that f100 (x) = (103)100 = 10300 whereas f(103) = 10103 = 101000
1
2158-2161
Our claim is that this function f grows faster than fn (x) = xn for any positive integer n For example, we can prove that 10x grows faster than f100 (x) = x100 For large values of x like x = 103, note that f100 (x) = (103)100 = 10300 whereas f(103) = 10103 = 101000 Clearly f (x) is much greater than f100 (x)
1
2159-2162
For example, we can prove that 10x grows faster than f100 (x) = x100 For large values of x like x = 103, note that f100 (x) = (103)100 = 10300 whereas f(103) = 10103 = 101000 Clearly f (x) is much greater than f100 (x) It is not difficult to prove that for all x > 103, f (x) > f100 (x)
1
2160-2163
For large values of x like x = 103, note that f100 (x) = (103)100 = 10300 whereas f(103) = 10103 = 101000 Clearly f (x) is much greater than f100 (x) It is not difficult to prove that for all x > 103, f (x) > f100 (x) But we will not attempt to give a proof of this here
1
2161-2164
Clearly f (x) is much greater than f100 (x) It is not difficult to prove that for all x > 103, f (x) > f100 (x) But we will not attempt to give a proof of this here Similarly, by choosing large values of x, one can verify that f(x) grows faster than fn (x) for any positive integer n
1
2162-2165
It is not difficult to prove that for all x > 103, f (x) > f100 (x) But we will not attempt to give a proof of this here Similarly, by choosing large values of x, one can verify that f(x) grows faster than fn (x) for any positive integer n Definition 3 The exponential function with positive base b > 1 is the function y = f (x) = bx The graph of y = 10x is given in the Fig 5
1
2163-2166
But we will not attempt to give a proof of this here Similarly, by choosing large values of x, one can verify that f(x) grows faster than fn (x) for any positive integer n Definition 3 The exponential function with positive base b > 1 is the function y = f (x) = bx The graph of y = 10x is given in the Fig 5 9
1
2164-2167
Similarly, by choosing large values of x, one can verify that f(x) grows faster than fn (x) for any positive integer n Definition 3 The exponential function with positive base b > 1 is the function y = f (x) = bx The graph of y = 10x is given in the Fig 5 9 It is advised that the reader plots this graph for particular values of b like 2, 3 and 4
1
2165-2168
Definition 3 The exponential function with positive base b > 1 is the function y = f (x) = bx The graph of y = 10x is given in the Fig 5 9 It is advised that the reader plots this graph for particular values of b like 2, 3 and 4 Following are some of the salient features of the exponential functions: (1) Domain of the exponential function is R, the set of all real numbers
1
2166-2169
9 It is advised that the reader plots this graph for particular values of b like 2, 3 and 4 Following are some of the salient features of the exponential functions: (1) Domain of the exponential function is R, the set of all real numbers (2) Range of the exponential function is the set of all positive real numbers
1
2167-2170
It is advised that the reader plots this graph for particular values of b like 2, 3 and 4 Following are some of the salient features of the exponential functions: (1) Domain of the exponential function is R, the set of all real numbers (2) Range of the exponential function is the set of all positive real numbers (3) The point (0, 1) is always on the graph of the exponential function (this is a restatement of the fact that b0 = 1 for any real b > 1)
1
2168-2171
Following are some of the salient features of the exponential functions: (1) Domain of the exponential function is R, the set of all real numbers (2) Range of the exponential function is the set of all positive real numbers (3) The point (0, 1) is always on the graph of the exponential function (this is a restatement of the fact that b0 = 1 for any real b > 1) (4) Exponential function is ever increasing; i
1
2169-2172
(2) Range of the exponential function is the set of all positive real numbers (3) The point (0, 1) is always on the graph of the exponential function (this is a restatement of the fact that b0 = 1 for any real b > 1) (4) Exponential function is ever increasing; i e
1
2170-2173
(3) The point (0, 1) is always on the graph of the exponential function (this is a restatement of the fact that b0 = 1 for any real b > 1) (4) Exponential function is ever increasing; i e , as we move from left to right, the graph rises above
1
2171-2174
(4) Exponential function is ever increasing; i e , as we move from left to right, the graph rises above Fig 5
1
2172-2175
e , as we move from left to right, the graph rises above Fig 5 9 Rationalised 2023-24 CONTINUITY AND DIFFERENTIABILITY 127 (5) For very large negative values of x, the exponential function is very close to 0
1
2173-2176
, as we move from left to right, the graph rises above Fig 5 9 Rationalised 2023-24 CONTINUITY AND DIFFERENTIABILITY 127 (5) For very large negative values of x, the exponential function is very close to 0 In other words, in the second quadrant, the graph approaches x-axis (but never meets it)
1
2174-2177
Fig 5 9 Rationalised 2023-24 CONTINUITY AND DIFFERENTIABILITY 127 (5) For very large negative values of x, the exponential function is very close to 0 In other words, in the second quadrant, the graph approaches x-axis (but never meets it) Exponential function with base 10 is called the common exponential function
1
2175-2178
9 Rationalised 2023-24 CONTINUITY AND DIFFERENTIABILITY 127 (5) For very large negative values of x, the exponential function is very close to 0 In other words, in the second quadrant, the graph approaches x-axis (but never meets it) Exponential function with base 10 is called the common exponential function In the Appendix A
1
2176-2179
In other words, in the second quadrant, the graph approaches x-axis (but never meets it) Exponential function with base 10 is called the common exponential function In the Appendix A 1
1
2177-2180
Exponential function with base 10 is called the common exponential function In the Appendix A 1 4 of Class XI, it was observed that the sum of the series 1 1 1
1
2178-2181
In the Appendix A 1 4 of Class XI, it was observed that the sum of the series 1 1 1 1
1
2179-2182
1 4 of Class XI, it was observed that the sum of the series 1 1 1 1 2
1
2180-2183
4 of Class XI, it was observed that the sum of the series 1 1 1 1 2 + + + is a number between 2 and 3 and is denoted by e
1
2181-2184
1 2 + + + is a number between 2 and 3 and is denoted by e Using this e as the base we obtain an extremely important exponential function y = ex
1
2182-2185
2 + + + is a number between 2 and 3 and is denoted by e Using this e as the base we obtain an extremely important exponential function y = ex This is called natural exponential function
1
2183-2186
+ + + is a number between 2 and 3 and is denoted by e Using this e as the base we obtain an extremely important exponential function y = ex This is called natural exponential function It would be interesting to know if the inverse of the exponential function exists and has nice interpretation
1
2184-2187
Using this e as the base we obtain an extremely important exponential function y = ex This is called natural exponential function It would be interesting to know if the inverse of the exponential function exists and has nice interpretation This search motivates the following definition
1
2185-2188
This is called natural exponential function It would be interesting to know if the inverse of the exponential function exists and has nice interpretation This search motivates the following definition Definition 4 Let b > 1 be a real number
1
2186-2189
It would be interesting to know if the inverse of the exponential function exists and has nice interpretation This search motivates the following definition Definition 4 Let b > 1 be a real number Then we say logarithm of a to base b is x if bx = a
1
2187-2190
This search motivates the following definition Definition 4 Let b > 1 be a real number Then we say logarithm of a to base b is x if bx = a Logarithm of a to base b is denoted by logb a
1
2188-2191
Definition 4 Let b > 1 be a real number Then we say logarithm of a to base b is x if bx = a Logarithm of a to base b is denoted by logb a Thus logb a = x if bx = a
1
2189-2192
Then we say logarithm of a to base b is x if bx = a Logarithm of a to base b is denoted by logb a Thus logb a = x if bx = a Let us work with a few explicit examples to get a feel for this
1
2190-2193
Logarithm of a to base b is denoted by logb a Thus logb a = x if bx = a Let us work with a few explicit examples to get a feel for this We know 23 = 8
1
2191-2194
Thus logb a = x if bx = a Let us work with a few explicit examples to get a feel for this We know 23 = 8 In terms of logarithms, we may rewrite this as log2 8 = 3
1
2192-2195
Let us work with a few explicit examples to get a feel for this We know 23 = 8 In terms of logarithms, we may rewrite this as log2 8 = 3 Similarly, 104 = 10000 is equivalent to saying log10 10000 = 4
1
2193-2196
We know 23 = 8 In terms of logarithms, we may rewrite this as log2 8 = 3 Similarly, 104 = 10000 is equivalent to saying log10 10000 = 4 Also, 625 = 54 = 252 is equivalent to saying log5 625 = 4 or log25 625 = 2
1
2194-2197
In terms of logarithms, we may rewrite this as log2 8 = 3 Similarly, 104 = 10000 is equivalent to saying log10 10000 = 4 Also, 625 = 54 = 252 is equivalent to saying log5 625 = 4 or log25 625 = 2 On a slightly more mature note, fixing a base b > 1, we may look at logarithm as a function from positive real numbers to all real numbers
1
2195-2198
Similarly, 104 = 10000 is equivalent to saying log10 10000 = 4 Also, 625 = 54 = 252 is equivalent to saying log5 625 = 4 or log25 625 = 2 On a slightly more mature note, fixing a base b > 1, we may look at logarithm as a function from positive real numbers to all real numbers This function, called the logarithmic function, is defined by logb : R+ → R x → logb x = y if by = x As before if the base b = 10, we say it is common logarithms and if b = e, then we say it is natural logarithms
1
2196-2199
Also, 625 = 54 = 252 is equivalent to saying log5 625 = 4 or log25 625 = 2 On a slightly more mature note, fixing a base b > 1, we may look at logarithm as a function from positive real numbers to all real numbers This function, called the logarithmic function, is defined by logb : R+ → R x → logb x = y if by = x As before if the base b = 10, we say it is common logarithms and if b = e, then we say it is natural logarithms Often natural logarithm is denoted by ln
1
2197-2200
On a slightly more mature note, fixing a base b > 1, we may look at logarithm as a function from positive real numbers to all real numbers This function, called the logarithmic function, is defined by logb : R+ → R x → logb x = y if by = x As before if the base b = 10, we say it is common logarithms and if b = e, then we say it is natural logarithms Often natural logarithm is denoted by ln In this chapter, log x denotes the logarithm function to base e, i
1
2198-2201
This function, called the logarithmic function, is defined by logb : R+ → R x → logb x = y if by = x As before if the base b = 10, we say it is common logarithms and if b = e, then we say it is natural logarithms Often natural logarithm is denoted by ln In this chapter, log x denotes the logarithm function to base e, i e
1
2199-2202
Often natural logarithm is denoted by ln In this chapter, log x denotes the logarithm function to base e, i e , ln x will be written as simply log x
1
2200-2203
In this chapter, log x denotes the logarithm function to base e, i e , ln x will be written as simply log x The Fig 5
1
2201-2204
e , ln x will be written as simply log x The Fig 5 10 gives the plots of logarithm function to base 2, e and 10
1
2202-2205
, ln x will be written as simply log x The Fig 5 10 gives the plots of logarithm function to base 2, e and 10 Some of the important observations about the logarithm function to any base b > 1 are listed below: Fig 5
1
2203-2206
The Fig 5 10 gives the plots of logarithm function to base 2, e and 10 Some of the important observations about the logarithm function to any base b > 1 are listed below: Fig 5 10 Rationalised 2023-24 MATHEMATICS 128 Fig 5
1
2204-2207
10 gives the plots of logarithm function to base 2, e and 10 Some of the important observations about the logarithm function to any base b > 1 are listed below: Fig 5 10 Rationalised 2023-24 MATHEMATICS 128 Fig 5 11 (1) We cannot make a meaningful definition of logarithm of non-positive numbers and hence the domain of log function is R+
1
2205-2208
Some of the important observations about the logarithm function to any base b > 1 are listed below: Fig 5 10 Rationalised 2023-24 MATHEMATICS 128 Fig 5 11 (1) We cannot make a meaningful definition of logarithm of non-positive numbers and hence the domain of log function is R+ (2) The range of log function is the set of all real numbers
1
2206-2209
10 Rationalised 2023-24 MATHEMATICS 128 Fig 5 11 (1) We cannot make a meaningful definition of logarithm of non-positive numbers and hence the domain of log function is R+ (2) The range of log function is the set of all real numbers (3) The point (1, 0) is always on the graph of the log function
1
2207-2210
11 (1) We cannot make a meaningful definition of logarithm of non-positive numbers and hence the domain of log function is R+ (2) The range of log function is the set of all real numbers (3) The point (1, 0) is always on the graph of the log function (4) The log function is ever increasing, i
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2208-2211
(2) The range of log function is the set of all real numbers (3) The point (1, 0) is always on the graph of the log function (4) The log function is ever increasing, i e
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2209-2212
(3) The point (1, 0) is always on the graph of the log function (4) The log function is ever increasing, i e , as we move from left to right the graph rises above
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2210-2213
(4) The log function is ever increasing, i e , as we move from left to right the graph rises above (5) For x very near to zero, the value of log x can be made lesser than any given real number
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2211-2214
e , as we move from left to right the graph rises above (5) For x very near to zero, the value of log x can be made lesser than any given real number In other words in the fourth quadrant the graph approaches y-axis (but never meets it)
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2212-2215
, as we move from left to right the graph rises above (5) For x very near to zero, the value of log x can be made lesser than any given real number In other words in the fourth quadrant the graph approaches y-axis (but never meets it) (6) Fig 5
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2213-2216
(5) For x very near to zero, the value of log x can be made lesser than any given real number In other words in the fourth quadrant the graph approaches y-axis (but never meets it) (6) Fig 5 11 gives the plot of y = ex and y = ln x
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2214-2217
In other words in the fourth quadrant the graph approaches y-axis (but never meets it) (6) Fig 5 11 gives the plot of y = ex and y = ln x It is of interest to observe that the two curves are the mirror images of each other reflected in the line y = x
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2215-2218
(6) Fig 5 11 gives the plot of y = ex and y = ln x It is of interest to observe that the two curves are the mirror images of each other reflected in the line y = x Two properties of ‘log’ functions are proved below: (1) There is a standard change of base rule to obtain loga p in terms of logb p
1
2216-2219
11 gives the plot of y = ex and y = ln x It is of interest to observe that the two curves are the mirror images of each other reflected in the line y = x Two properties of ‘log’ functions are proved below: (1) There is a standard change of base rule to obtain loga p in terms of logb p Let loga p = α, logb p = β and logb a = γ
1
2217-2220
It is of interest to observe that the two curves are the mirror images of each other reflected in the line y = x Two properties of ‘log’ functions are proved below: (1) There is a standard change of base rule to obtain loga p in terms of logb p Let loga p = α, logb p = β and logb a = γ This means aα = p, bβ = p and bγ = a