Question

Решите пожалуйста упр 284-285​

Answer 1

Ответ:

$\cos( \alpha + \beta ) + \cos( \frac{\pi}{2} - \alpha ) \cos( \frac{\pi}{2} - \beta ) = \cos( \alpha ) \cos( \beta ) - \sin( \alpha ) \sin( \beta ) + \sin( \alpha ) \sin( \beta ) = \cos( \alpha ) \cos( \beta )$

$\sin( \frac{\pi}{2} - \alpha ) \sin( \frac{\pi}{2} - \beta ) - \cos( \alpha - \beta ) = \cos( \alpha ) \cos( \beta ) - \cos( \alpha - \beta )$

$\sin(73) \cos(17) + \cos(73) \sin(17) = \sin(90) = 1$

$\sin(73) \cos(13) - \cos(73) \sin(13) = \sin(60) = \frac{ \sqrt{3} }{2}$

$\sin( \frac{5\pi}{12} ) \cos( \frac{\pi}{12} ) + \sin( \frac{\pi}{12} ) \cos( \frac{5\pi}{12} ) = \sin( \frac{\pi}{2} ) = 1$

$\sin( \frac{7\pi}{12} ) \cos( \frac{\pi}{12} ) - \sin( \frac{\pi}{12} ) \cos( \frac{7\pi}{12} ) = \sin( \frac{\pi}{2} ) = 1$