Half-angle formula for tan(A/2)

1. A.
   $\frac{\sqrt{1 + \cos A}}{\sqrt{1 - \cos A}}$
2. B.
   $\frac{\sqrt{1 - \sin A}}{\sqrt{1 + \cos A}}$
3. C.
   $\frac{\sqrt{1 - \cos A}}{\sqrt{1 + \cos A}}$
4. D.
   $\frac{\sqrt{\cos A - 1}}{\sqrt{1 + \cos A}}$

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1. A.
   $\frac{\cos\theta}{1 - \sin\theta}$
2. B.
   $\frac{\sin\theta}{1 - \cos\theta}$
3. C.
   $\frac{\cos\theta}{1 - \cos\theta}$
4. D.
   $\frac{\sin\theta}{1 + \cos\theta}$

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