Question

$cos{30}^{\circ }cos{60}^{\circ }-sin{30}^{\circ }sin{60}^{\circ }$= __________________

• A. -1
• B. 0
• C. 1
• D. 2

Answer 1

The correct option is B

0

$cos{30}^{\circ }cos{60}^{\circ }-sin{30}^{\circ }sin{60}^{\circ }$

= $\left(\frac{\sqrt{3}}{2}\right)\left(\frac{1}{2}\right)-\left(\frac{1}{2}\right)\left(\frac{\sqrt{3}}{2}\right)$

=$\frac{\sqrt{3}}{4}-\frac{\sqrt{3}}{4}$

=0

Hence (B)