Question

Найдите cos a если sin a = - 2/3 ​

Answer 1

Ответ:

Объяснение:

sin²α+cos²α=1;

cosα=√(1-sin²α)=√(1-(-2/3)²)=√(1-4/9)=√(5/9)=√5/3.

Answer 2

$sin {}^{2} a + cos {}^{2} a = 1$;

$cosa = \sqrt{} (1 - sin {}^{2} a) = \sqrt{} (1 - ( - \frac{2}{3} {}^{2} ) = \sqrt{} (1 - \frac{4}{9} ) = \sqrt{} ( \frac{5}{9} ) = \sqrt{} \frac{5}{3}$