# The value of cos1°

Question:

The value of $\cos 1^{\circ} \cos 2^{\circ} \cos 3^{\circ}\|.\| \cos 179^{\circ}$ is

(a) $\frac{1}{\sqrt{2}}$

(b) 0

(c) 1

(d) $-1$

Solution:

$\cos 1^{\circ} \cos 2^{\circ} \cos 3^{\circ} \ldots \cos 179^{\circ}$

$=\cos 1^{\circ} \cos 2^{\circ} \cos 3^{\circ} \ldots \cos 90^{\circ} \ldots \cos 179^{\circ}$

$=0 \quad\left(\cos 90^{\circ}=0\right)$

Hence, the correct answer is option B.