Oral Questions: 1. What are the formula for sin A, cos A and tan A? 2. What are the inverses of sin A, cos A and tan A known as? 3. What is the formula of cosec A, sec A and cot A? C.W. Questions 1. If sec θ = 5/4, show that (sinθ - 2cosθ)/(tanθ - cotθ) = 12/7 Ans : b = 4k, h = 5k Hence p = 3k Hence sin θ = 3/5 cos θ = 4/5 tan θ = 3/4 cot θ = 4/3 LHS = (sin θ - 2cos θ )/(tan θ - cot θ ) = (3/5 - 8/5)/(3/4-4/3) =( -1)/ (-7/12) = 12/7 = RHS 2. If tan θ = 1/√7, show that (cosec^2 θ- sec^2 θ) /(cosec^2 θ + sec^2 θ) = 3/4 3. If cosec θ = 2, show that (cot θ + sin θ ----------- ) = 2 1+cos θ 4. In ∆ABC, right angled at B, AB = 12cm and BC = 5 cm. Find the ...