Integration or anti differentiation is the process of finding a function given the derivative is already known. It essentially is and can be thought of as finding the derivative in reverse.

## Integration Rules

If we assume that:

$F'(x)=f(x)$

Then we can write the integral of f(x) as:

$\int{f(x)}dx=F(x)+C$

Where C is an arbitrary constant that defines the function F(x) which cannot be calculated from the function f(x)

### Definite Integral

The definite integral can be calculated as

$\int\limits_{a}^{b}{f(x)}dx=F(b)-F(a)$

Here we can see that if we left in the arbitrary constant for the definite integral it would cancel out as we minused F(a) from F(b).