2bjcos
Trigonometry
The cosine of the double angle is equal to the square of cosine of the angle minus the square of sine of the angle.
\cos 2\alpha = \cos^2 \alpha - \sin^2 \alpha
or
The cosine of the double angle is equal to the square of cosine of the angle minus the square of sine of the angle.
\cos 2\alpha = \cos^2 \alpha - \sin^2 \alpha
or