Question

вычеслить значение cos a, если sin a=1/2 и 0

Answer 1

$\cos \alpha = ± \sqrt{1 - \sin {}^{2} \alpha } = ± \sqrt{1 - ( \frac{1}{2} ) {}^{2} } = ± \sqrt{1 - \frac{1}{4} } = ± \sqrt{ \frac{3}{4} } = ± \frac{ \sqrt{3} }{2} ;$

$\cos \alpha = ± \sqrt{1 - \sin {}^{2} \alpha } = ± \sqrt{1 - 0 {}^{2} } = ± \sqrt{1 - 0} = ± \sqrt{1} = ± 1.$