The integral function is

Rewrite the integral function is

Assume .

Apply derivative on each side with respect to .

Substitutes and in equation .

Let

Apply derivative on each side with respect to .

Substitute and  in the integral function.

Trignometric property :  .

Integral formula :

.

Consider .

For a right triangle, and 

then .

Substitute the corresponding values in the integral function.

Substitute in the integral function.

, where .

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