Question

If $\sin {\theta }_1+\sin {\theta }_2+\sin {\theta }_3=3,0^o<{\theta }_1,{\theta }_2,{\theta }_3<{90}^o$, find the value of $\cos {\theta }_1+\cos {\theta }_2+\cos {\theta }_3$.

Answer 1

$\begin{array}{c}\sin {\theta }_1+\sin {\theta }_2+\sin {\theta }_3=3\\ if{\theta }_1={\theta }_2={\theta }_3=\frac{1}{2}\\ \cos {\theta }_1+\cos {\theta }_2+\cos {\theta }_3=?\\ \cos \frac{\pi }{2}+\cos \frac{\pi }{2}+\cos \frac{\pi }{2}=0\end{array}$