Answer:
Step-by-step explanation:
Hint: 1- 2sin²x = Cos 2x
LHS = 1 - 2Sin² (π/4 - Ф/2)
= Cos 2 *(π/4 - Ф/2)
= Cos 2*π/4 - 2*Ф/2
= Cos π/2 - Ф
= Sin Ф = RHS
RHS=sinA
LHS=1-2sin^2(45-A/2)
=cos2(45-A/2)
=cos(90-A)
=sinA proved.
