This video lecture from Trigonometric Identities (F.Sc. first year Mathematics) covers: Question number 13-14 of exercise 10.2. In these questions we are given that the sum of alpha, beta and gamma is 180, using this information we prove the given trigonometric equation and we express the given expression in the form of rsine(theta + phi). 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.