Question

преобразуйте в сумму

$sin 3x cos 9x$

sin 32° sin58°

Answer 1

1.
$\sin(3x) \times \cos(9x) = \frac{1}{2} ( \sin(3x - 9x) + \sin(3x + 9x) ) = \frac{1}{2} ( \sin12x - \sin6x )$
2.
$\frac{1}{2} ( \cos(32 - 58) - \cos(32 + 58) ) = \frac{1}{2} ( \cos( - 26) - \cos(90) ) = \frac{1}{2} ( \cos(26) - 0) = \frac{1}{2} \cos(26)$