Half-angle formulas
We found 8 formulas for half-angle
Expressing trigonometric functions of an angle $\dfrac{x}{2}$ in terms of functions of an angle $x$.
1.
Half Angle Formula of Sine
$\sin \dfrac{\alpha}{2} = \pm \sqrt{\dfrac{1-\cos\alpha}{2}}$
2.
Half Angle Formula of Cosine
$\cos \dfrac{\alpha}{2} = \pm \sqrt{\dfrac{1+\cos\alpha}{2}}$
3.
Half Angle Formula of Tangent
$\tan\dfrac{\alpha}{2} = \pm \sqrt{\dfrac{1-\cos\alpha}{1+\cos\alpha}}$
4.
Half Angle Formula of Tangent
$\tan \dfrac{\alpha}{2} = \dfrac{\sin\alpha}{1+\cos\alpha}$
5.
Half Angle Formula of Tangent
$\tan\dfrac{\alpha}{2} = \dfrac{1-\cos\alpha}{\sin\alpha}$
6.
Half Angle Formula of Cotangent
$\cot \dfrac{\alpha}{2} = \pm \sqrt{\dfrac{1+\cos\alpha}{1-\cos\alpha}}$
7.
Half Angle Formula of Cotangent
$\cot\dfrac{\alpha}{2} = \dfrac{\sin\alpha}{1-\cos\alpha}$
8.
Half Angle Formula of Cotangent
$\cot \dfrac{\alpha}{2} = \dfrac{1+\cos\alpha}{\sin\alpha}$