The function is .

Rewrite the integral as .

Assume .

.

Apply derivative on each side with respect to .

.

Rewrite the expression using chain rule.

.

Fundamental theorem of calculus: 

If  is continuous on , then the function  is defined by  is continuous on  and differentiable on , then .

Here .

Therefore, .

.

Replace  in above expression.

.

The derivative of the function is .