Sinus

Die Definition lautet $\sin \left(x\right)=\frac{e^{xi}-e^{-xi}}{2i},\cos (x)=\frac{e^{ix}+e^{-ix}}{2}$ Die Additionstheoreme sind: $\begin{array}{rl}& \sin (x+y)=\sin (x)\cos (y)+\cos (x)\sin (y)\\ & \cos (x+y)=\cos (x)\cos (y)-\sin (x)\cos (y)\\ \end{array}$