Question

Вызначте tga, когда cosa =-4/5 и пи/2

Answer 1

$\displaystile\bf\\Cos\alpha =-\frac{4}{5} \ \ ;\ \ \frac{\pi }{2}$

Второй :

$\displaystyle\bf\\Sin\alpha =\sqrt{1-Cos^{2}\alpha } =\sqrt{1-\Big(-\frac{4}{5} \Big)^{2} } =\sqrt{1-\frac{16}{25} } =\sqrt{\frac{9}{25} } =\frac{3}{5} tg\alpha =\frac{Sin\alpha }{Cos\alpha } =\frac{3}{5} :\Big(-\frac{4}{5} \Big)=-\frac{3}{5} \cdot\frac{5}{4}=-\frac{3}{4} =-0,75$