$\newcommand{\dede}[2]{\frac{\partial #1}{\partial #2} }
\newcommand{\dd}[2]{\frac{d #1}{d #2}}
\newcommand{\divby}[1]{\frac{1}{#1} }
\newcommand{\typing}[3][\Gamma]{#1 \vdash #2 : #3}
\newcommand{\xyz}[0]{(x,y,z)}
\newcommand{\xyzt}[0]{(x,y,z,t)}
\newcommand{\hams}[0]{-\frac{\hbar^2}{2m}(\dede{^2}{x^2} + \dede{^2}{y^2} + \dede{^2}{z^2}) + V\xyz}
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\newcommand{\ham}[0]{-\frac{\hbar^2}{2m}(\dede{^2}{x^2}) + V(x)}$
### Trigonometry, Trigonomecry
Die wichtigsten Sätze:
$cos^{2}+ sin^{2} = 1$
$cos = \frac{e^{ix}+e^{-ix}}{2}$
$sin = \frac{e^{ix}-e^{-ix}}{2i}$
$tan = \frac{sin}{cos}$
$\sin(a+b) = \sin a \cos b + \sin b \ cos a$
$\cos(a+b) = \cos a \cos b - \sin a \sin b$
$\sin a + \sin b = 2 \sin \left(\frac{a+b}{2}\right) \cos \left(\frac{a-b}{2}\right)$
$\cos a + \cos b = 2 \cos \left(\frac{a+b}{2}\right) \cos \left( \frac{a-b}{2} \right)$