Question

$\cos 1^{\circ }\cdot \cos 2^{\circ }\cdot \cos 3^{\circ }\dots \dots \cos 179^{\circ }=$

• A. 0
• B. 1
• C. $-\frac{1}{2}$
• D. -1

Answer 1

Answer: (A)

$\cos 1^{\circ }\cdot \cos 2^{\circ }\cdot \cos 3^{\circ }\dots .$
$\cos 90^{\circ }\cos 91^{\circ }\dots ..\cos 179^{\circ }$
$=0\left[\because \cos 90^{\circ }=0\right]$