This video lecture from Trigonometric Identities (F.Sc. first year Mathematics) covers: Question numbers 5 of exercise 10.1. In this question we prove the given trigonometric equations if alpha, beta and gamma are three angles of a triangle. Find more e-learning material and educational video lectures in Urdu at maktab.pk. These videos are free to use for promotional and commercial purpose by keeping the credits to Maktab.