Question

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

Answer 1

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