(ii)
This theorem is very useful, because it gives us a method of calculating the
definite integral more easily, without calculating the limit of a sum (iii)
The crucial operation in evaluating a definite integral is that of finding a function
whose derivative is equal to the integrand This strengthens the relationship
between differentiation and integration (iv)
In 
( )
b
∫a f x dx
, the function f needs to be well defined and continuous in [a, b]