# cosine at multiples of straight angle

Everybody remembers the cosine values

 $\cos 0=1,\quad\cos(\pm\pi)=-1,\quad\cos(\pm 2\pi)=1,\quad\cos(\pm 3\pi)=-1,\,% \,...$

The thing can be concisely expressed as the

 $\cos{n\pi}=(-1)^{n}$

for each integer $n$.  The values of sine at the same angles are simply 0.

 Title cosine at multiples of straight angle Canonical name CosineAtMultiplesOfStraightAngle Date of creation 2013-03-22 15:45:40 Last modified on 2013-03-22 15:45:40 Owner pahio (2872) Last modified by pahio (2872) Numerical id 6 Author pahio (2872) Entry type Definition Classification msc 26A09 Related topic multiple Related topic ComplexSineAndCosine Related topic HigherOrderDerivativesOfSineAndCosine Related topic FourierSineAndCosineSeries Related topic GeneralAssociativity Related topic ValueOfRiemannZetaFunctionAtS4 Related topic ValueOfDirichletEtaFunctionAtS2