$cos\, \frac{\pi }{{10}} \,cos\, \frac{2\pi }{{10}} \,cos\,\frac{4\pi }{{10}}\, cos\,\frac{8\pi }{{10}}\, cos\,\frac{16\pi }{{10}}$ =
$cos\, \frac{\pi }{{10}} \,cos\, \frac{2\pi }{{10}} \,cos\,\frac{4\pi }{{10}}\, cos\,\frac{8\pi }{{10}}\, cos\,\frac{16\pi }{{10}}$ =
- A
$\frac{1 }{{32}}$
- B
$\frac{1}{{16}}$
- C
$\frac{{\cos \,\,\left( {\pi /10} \right)}}{{16}}$
- D
$-\frac{{\sqrt {10\,\, + \,\,2\sqrt 5 } }}{{64}}$
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