Let $\alpha, \beta$ be such that $\pi < \alpha - \beta < 3 \pi$.

If $\sin \alpha + \sin \beta = -\frac {21}{65}$ and $\cos \alpha + \cos \beta = -\frac {27}{65}$, then $\cos (\frac {\alpha - \beta}{2})$ is

The calculations are pretty complex, so I advise you to go open a calculator.

This problem is part of the set Trigonometry.

×

Problem Loading...

Note Loading...

Set Loading...