This is a Test of Mathematics Solution Subjective 115 (from ISI Entrance). The book, Test of Mathematics at 10+2 Level is Published by East West Press. This problem book is indispensable for the preparation of I.S.I. B.Stat and B.Math Entrance.

If , then show that

Put .

The given expression reduces to

Hence replacing in the required expression we get

**(Proved)**

**What is this topic:**Trigonometry**What are some of the associated concept:**Change of Variables**Where can learn these topics:**Cheenta**Book Suggestions:**Trigonometry Volume I by S.L. Loney