Question

Найдите значение выражения: cos^2 87(градусов)+cos^2 177(градусов)

Answer 1

$\displaystyle cos^287`+cos^2177`=cos^2(90`-3`)+cos^2(180`-3`)=\\\\=(cos(\frac{\pi }{2}-3`))^2 +(cos(\pi -3`))^2=(sin3`)^2+(-cos 3`)^2=\\\\=sin^23`+cos^23`=1$