Question

If $\sin {\theta }_1+\sin {\theta }_2+\sin {\theta }_3=3$ then $\cos {\theta }_1+\cos {\theta }_2+\cos {\theta }_3$=.................

• A. $3$
• B. $2$
• C. $1$
• D. $0$

Answer 1

The correct option is D $0$

$\sin {\theta }_1+\sin {\theta }_2+\sin {\theta }_3=3$
$\sin {\theta }_1=\sin {\theta }_2=\sin {\theta }_3=1$
$\therefore {\theta }_1+{\theta }_2+{\theta }_3=\frac{\pi }{2}$
$\therefore \cos {\theta }_1+\cos {\theta }_2+\cos {\theta }_3=0$