If $x = \cos 10^\circ \cos 20^\circ \cos 40^\circ ,$ then the value of $x$ is
If $x = \cos 10^\circ \cos 20^\circ \cos 40^\circ ,$ then the value of $x$ is
- A
$\frac{1}{4}\tan 10^\circ $
- B
$\frac{1}{8}\cot 10^\circ $
- C
$\frac{1}{8}{\rm{cosec}}10^\circ $
- D
$\frac{1}{8}\sec 10^\circ $
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- [IIT 1980]