Question

The value of $\left|\begin{array}{cc}sin10^{\circ }& -cos10^{\circ }\\ sin80^{\circ }& cos80^{\circ }\end{array}\right|$ is

• A. -1
• B. 1
• C. 2
• D. 0

Answer 1

Answer: (B)

Consider, $\left|\begin{array}{cc}sin10^{\circ }& -cos10^{\circ }\\ sin80^{\circ }& cos80^{\circ }\end{array}\right|$
$=sin10^{\circ }cos80^{\circ }+\sin 80^{\circ }cos10^{\circ }$
$-\sin \left(10^{\circ }+80^{\circ }\right)-\sin \left(90^{\circ }\right)-1$