[tex]\bf \textit{Double Angle Identities} \\\\ \underset{\underset{\textit{notice here}}{\uparrow }}{sin(2\theta)=2sin(\theta)cos(\theta)} ~\hfill cos(2\theta)= \begin{cases} cos^2(\theta)-sin^2(\theta)\\ 1-2sin^2(\theta)\\ 2cos^2(\theta)-1 \end{cases} \\\\\\ tan(2\theta)=\cfrac{2tan(\theta)}{1-tan^2(\theta)}[/tex]
