Question

Найдите sin a, если cos a =0.3 и 0 ≤ a ≤ π/2

Answer 1

$sin^2alpha+cos^2alpha=1\\sin^2alpha+0,3^2=1\\sin^2alpha+0,09=1\\sin^2alpha=1-0,09\sin^2alpha=0,91\\sinalpha=sqrt{0,91}\\sinalpha=frac{sqrt{91}}{10}$