\(\cos(2x) = 2 \cos(x)\)

\(\sin(2x) = 2 \sin(x)\)

\(\sin(2x) = \dfrac {\cot(x) - \tan(x)}{2}\)

\(\cos(2x) = \dfrac {\cot(x) - \tan(x)}{2}\)

\(\cos(2x) = 2 \sin(x) \cdot \cos(x)\)

\(\sin(2x) = 2 \sin(x) \cdot \cos(x)\)