Question

if sin theta +sin square theta =1 then find the value of cos square theta + cos four theta

Answer 1

SinA+Sin2A= 1
= sinA = 1-sin2A = cos2A.... (1)
Cos2A+cos4A
= cos2A+(cos2A) 2.
= cos2A+(sinA) 2. ...... Using (1)
= cos2A + sin2A
= 1.