Question

Найдите значение выражения
$\frac{15}{ { \sin }^{2}72 + { \sin }^{2}18 }$
72 и 18 в градусах​

Answer 1

$\frac{15}{ \sin {}^{2} (72 \degree) + \sin ^{2} (18 \degree) } = \frac{15}{ \sin^2(90 \degree - 18 \degree) + \sin {}^{2} (18 \degree) } = \frac{15}{ \cos {}^{2} (18 \degree) + \sin {}^{2} (18 \degree) } = \frac{15}{1} = 15$