Section 5 Mathematical Formulas

5-1 Trigonometric Function

5-1-6 Half-angle Formula

$sin\frac{\theta}{2}=\pm\sqrt{\frac{1-cos\theta}{2}}$	$cos\frac{\theta}{2}=\pm\sqrt{\frac{1+cos\theta}{2}}$	$tan\frac{\theta}{2}=\pm\sqrt{\frac{1-cos\theta}{1+cos\theta}}$
$　$	$　$	$\;\;\;\;\;\;\;\;\;\;=\frac{sin\theta}{1+cos\theta}$
$　$	$　$	$\;\;\;\;\;\;\;\;\;\;=\frac{1-cos\theta}{sin\theta}$

　　　　　

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