Question

3. If cos + cos2 = 1, then sin2 + sin4 is ____________ (a)−1 (b)0 (c) 1 (d) 2

Answer 1

Answer:

cos A+cos^2 A=1 ————(1)

cos A =1-cos^2 A

[sin^2 A=1- cos^2 A]

cos A= sin^2 A ———-(2)

Substitute value of cos A in Eqn. (1)

(sin^2 A) + (sin^2 A)^2=1

sin^2 A + sin^4 A=1 [Proved]