The integral is .

Consider . 

Apply derivative on each side.  

Substitute and in the integral.

Replace in above expression.

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Consider the anti derivative function as and integrand function as .

Take , then .

Graph :

Graph the integrand function and anti derivative function.

Observe the graph, 

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

Hence the curve is derivative of the curve .

Therefore, is antiderivative of the integrand function .

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