Question:
The value of $\cos 1^{\circ} \cos 2^{\circ} \cos 3^{\circ}$ $\cos 180^{\circ}$ is
(a) 1
(b) 0
(c) $-1$
(d) None of these
Solution:
Here we have to find: $\cos 1^{\circ} \cos 2^{\circ} \cos 3^{\circ} \ldots \cos 180^{\circ}$
$\cos 1^{\circ} \cos 2^{\prime \prime} \cos 3^{\circ} \ldots \cos 180^{\prime \prime}$
$=0$
Hence the correct option is (b)