Goniometrie
\begin{aligned} & \sin (t+u)=\sin (t) \cos (u)+\cos (t) \sin (u) \\ & \sin (t-u)=\sin (t) \cos (u)-\cos (t) \sin (u) \\ & \cos (t+u)=\cos (t) \cos (u)-\sin (t) \sin (u) \\ & \cos (t-u)=\cos (t) \cos (u)+\sin (t) \sin (u) \\ & \sin (2 t)=2 \sin (t) \cos (t) \\ & \cos (2 t)=\cos ^{2}(t)-\sin ^{2}(t)=2 \cos ^{2}(t)-1=1-2 \sin ^{2}(t) \end{aligned}