This video lecture from Differentiation (F.Sc. second year Mathematics) covers: Questions 4-6 of exercise 2.5. In these questions we find derivative of trigonometric functions with respect to x, find derivative of one trigonometric function with respect to another trigonometric function by using chain rule, prove a differential equation from given trigonometric equation. 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.