$\tan \frac{A}{2}$ is equal to
$\tan \frac{A}{2}$ is equal to
- A
$ \pm \sqrt {\frac{{1 - \sin A}}{{1 + \sin A}}} $
- B
$ \pm \sqrt {\frac{{1 + \sin A}}{{1 - \sin A}}} $
- C
$ \pm \sqrt {\frac{{1 - \cos A}}{{1 + \cos A}}} $
- D
$ \pm \sqrt {\frac{{1 + \cos A}}{{1 - \cos A}}} $
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