Question

Найдите значение выражения -30/(сos^2 87 + cos^2 177)

Answer 1

$frac{-30}{cos^{2}87 + cos^{2}177} =frac{-30}{cos^{2}(90- 3)+cos^{2}(180-3)} =$

$=frac{-30}{sin^{2}3 + cos^{2}3} =frac{-30}{1}=-30$