Question

Evaluate $\left|\begin{array}{ll}\cos 15 & \sin 15 \\\ \sin 75 & \cos 75\end{array}\right|$

• A. 1
• B. 0
• C. 2
• D. 3

Answer 1

Answer: (B)

0

Answer 2

$\begin{vmatrix} {\cos 15}&{\sin 15} \\\ {\sin 75}&{\cos 75} \end{vmatrix}$
$= cos 15 cos 75 - sin 15 sin 75$
$= cos (15 + 75) = cos\, 90 = 0$