Question

The value of $\cos 1°\cos 2°\cos 3°...\cos 179°$ is

(a) $\frac{1}{\sqrt{2}}$ (b) 0 (c) 1 (d) $-1$

Answer 1

$$\begin{gathered} \cos 1°\cos 2°\cos 3°...\cos 179° \\ =\cos 1°\cos 2°\cos 3°...\cos 90°...\cos 179° \\ =0\left(\cos 90°=0\right) \end{gathered}$$

Hence, the correct answer is option B.