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.
$frac{1}{2} ( cos(32 - 58) - cos(32 + 58) ) = frac{1}{2} ( cos( - 26) - cos(90) ) = frac{1}{2} ( cos(26) - 0) = frac{1}{2} cos(26)$