三角関数 - niming538の日記

p.31 加法定理
$\sin (\alpha + \beta) = \sin \alpha \cos \beta + \cos \alpha \sin \beta$
$\cos (\alpha + \beta) = \cos \alpha \cos \beta - \sin \alpha \sin \beta$
$\sin (\alpha - \beta) = \sin \alpha \cos \beta - \cos \alpha \sin \beta$
$\cos (\alpha - \beta) = \cos \alpha \cos \beta + \sin \alpha \sin \beta$

$\tan (\alpha + \beta) = \frac{\tan \alpha + \tan \beta}{1 - \tan \alpha \tan \beta}$
$\tan (\alpha - \beta) = \frac{\tan \alpha - \tan \beta}{1 + \tan \alpha \tan \beta}$