Question

1. Найдите ctg α, если tg α = 0,5
2. Найдите sin α, если cos α = -0,6 и π < a < $\frac{3\pi }{2}$

Answer 1

$1)tg\alpha=0,5=\dfrac{1}{2}\\\\Ctg\alpha=\dfrac{1}{tg\alpha }=\dfrac{1}{\dfrac{1}{2} } =2\\\\\boxed{Ctg\alpha=2} \\\\\\2)\pi<\alpha <\dfrac{3\pi }{2} \ \Rightarrow \ Sin\alpha <0\\\\Sin\alpha=-\sqrt{1-Cos^{2}\alpha}=-\sqrt{1-(-0,6)^{2} }=-\sqrt{1-0,36}=\\\\=-\sqrt{0,64}=-0,8\\\\\boxed{Sin\alpha=-0,8}$