# 10.4: Mathematical Formulas - Trigonometry

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$e ^ { j \theta } = \cos \theta + j \sin \theta \nonumber$

$\cos \theta = \frac { 1 } { 2 } \left( e ^ { j \theta } + e ^ { - j \theta } \right) \nonumber$

$\sin \theta = \frac { 1 } { j 2 } \left( e ^ { j \theta } - e ^ { - j \theta } \right) \nonumber$

$\cos ^ { 2 } \theta = \frac { 1 } { 2 } + \frac { 1 } { 2 } \cos 2 \theta \nonumber$

$\sin ^ { 2 } \theta = \frac { 1 } { 2 } - \frac { 1 } { 2 } \cos 2 \theta \nonumber$

This page titled 10.4: Mathematical Formulas - Trigonometry is shared under a CC BY-SA 4.0 license and was authored, remixed, and/or curated by Steven W. Ellingson (Virginia Tech Libraries' Open Education Initiative) .