Question

If A = 30^o, then prove that :

2 cos² A - 1 = 1 - 2 sin²A

Answer 1

Given A = 30°

2 cos² A – 1 = 2 cos² 30° – 1

=`2(3/4) – 1`

= `(3)/(2) – 1`

= `(1)/(2)`

1 - 2 sin²A = 1 - 2 sin² 30°

= 1 - 2`(1/4)`

= `1/2`

∴ 2 cos²A – 1 = 1 – 2 sin²A