� We have defined
( )
b
∫a f x dx
 as the area of the region bounded by the curve
y = f (x), a ≤ x ≤ b, the x-axis and the ordinates x = a and x = b Let x be a
given point in [a, b] Then 
( )
x
∫a f x dx
 represents the Area function A (x) This concept of area function leads to the Fundamental Theorems of Integral
Calculus