If $\sin \alpha = \frac{{ - 3}}{5},$ where $\pi < \alpha < \frac{{3\pi }}{2},$ then $\cos \frac{1}{2}\alpha = $
If $\sin \alpha = \frac{{ - 3}}{5},$ where $\pi < \alpha < \frac{{3\pi }}{2},$ then $\cos \frac{1}{2}\alpha = $
- A
$\frac{{ - 1}}{{\sqrt {10} }}$
- B
$\frac{1}{{\sqrt {10} }}$
- C
$\frac{3}{{\sqrt {10} }}$
- D
$\frac{{ - 3}}{{\sqrt {10} }}$
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