Question

If sinA + sin2A=1,then find the value of expression (cos2A+cos4A)

Answer 1

Answer:

By sq. Sin A + sin2A =1

Sin2A + Sin4A +2sinASin2A =1

1-cos2A + 1 -cos4A +2sin3A =1

2 - ( cos2A + cos4A ) +2 ( 1 ) = 1

2 + 2 -1 = cos2A + cos4A = 3