The integral is .

Consider . 

Apply derivative on each side.

Substitute and  in .

.

Replace in above expression.

.

. 

Consider the anti derivative function as .

and integrand function as . 

Take , .

Graph the integrand function and anti derivative function.

Observe the graph, 

When is negative, then is decreasing and when is positive , then is increasing.

Hence the curve is derivative of the curve .

Therefore, is antiderivative of the integrand function .  

.