Question

X = -135°, cos 2x = _______

1 - 2 sin^2 x
1 - 2 sin x
1 + 2 sin^2 x
1 + 2 sin x

Answer 1

cos 2 x=1-sin^2 x

Explanation:

x=-135°

cos 2x=cos (-270)=cos (-270+360)=cos 90=0

or cos 2x=1-2sin ²x=1-2(sin (-135))²

=1-2(-sin 135)²

=1-2(sin 135)²

=1-2(sin (180-45))²

=1-2(sin²45)

=1-2 (\frac{1}{\sqrt{2}})²

=1-1

=0