Question

If $sin \alpha +sin^{2} \alpha +sin^{3} \alpha =1$
 then $cos^{6} \alpha - 4cos^{4} \alpha +8cos^{2} \alpha =$

Answer 1

sinx+sin2x=1
sinx=1-sin2x
sinx=cos2x(squaring both the sides)
sin2x=cos4x
1-cos2x=cos4x
1=cos4x+cos2x

i think you got the idea