The integral is .

(a)

Let ,

.

Consider .

Substiute the corresponding values in the integral.

.

Trignometric identity : .

.

.

Draw a triangle from the trignometric substitution.

From the figure, .

.

(b).

The limits obtained by the trignometric substitution are

 if .

When .

.

(a)

By the integration limits :

.

(b)

By the limits obtained by the trignometric substitution:

.