Question

. If sin θ + sin² θ = 1, then cos² θ + cos4 θ = ..
(a) -1
(b) 0
(c) 1
(d) 2​

Answer 1

Answer:

cos² θ + cos4 θ =  (c)1

Step-by-step explanation:

sin² θ = 1 - sinθ ------(1)

we know that

sin² θ + cos² θ = 1

1-sinθ + cos² θ = 1 (using 1)

cos² θ = 1 - (1 - sinθ)

cos² θ = 1 - 1 + sinθ

cos² θ = sinθ -------(2)

cos² θ + cos4 θ = sinθ + sin² θ = 1 (using 2)