If cos θ + cos2θ = 1, then find the value of expression (sin2θ + sin4θ).
Answer:
1
- It is given that
cos θ + cos2θ = 1 ............. Eq. (1) - Above equation can be re-written as following
⇒ 1 - cos2θ = cos θ - Since 1 - cos2θ = sin2θ, we can re-write equation as following,
⇒ sin2θ = cos θ ............. Eq. (2) - Now replace value of sin2θ = cos θ, in required expression
sin2θ + sin4θ = cos θ + cos2θ
⇒ sin2θ + sin4θ = 1 .................... Using Eq. (1)