Question

If sinA + sin2A = 1 then what is the value of cos2A + cos4A ?

A) 1 B) 2 C) 1/2 D) 1/4

Answer 1

1

Step-by-step explanation:

sina + sin²a = 1

sina = 1 - sin²a

sina = cos²a ------‐-(1)

sin²a = cos⁴a-------(2)

Hence

cos²a + cos⁴a = 1 --------------(from 1 & 2)