A definite integral is denoted by 
( )
b
∫a f x dx
, where a is called the
lower limit of the integral and b is called the upper limit of the integral The definite
integral is introduced either as the limit of a sum or if it has an anti derivative F in the
interval [a, b], then its value is the difference  between the values of F at the end
points, i e , F(b) – F(a)