Question

Question #df912

Answer 1

`cos^6 A + sin^6A`

`=(cos^2A)^3 + (sin^2A)^3`

`=(cos^2A +sin^2A)^3-3cos^2Asin^2A(cos^2+sin^2A)`

`=1^3-3/4*4cos^2A*sin^2A*1`

`=1-3/4*(2cosA*sinA)^2`

`=1-3/4*(sin2A)^2`

`=1-3/4*sin^2 2A=RHS`

Proved