Question

cos β= 45 3π2<β<2π 
найти:sinβ,tgβ,ctgβ

Answer 1

$cos^2 beta+sin^2 beta=1$
$frac{3pi}{2}<beta<2pi$ => $sin beta<0$
$sin beta=-sqrt{1-cos^2 beta}=\\-sqrt{1-(frac{4}{5})^2}=frac{3}{5}$
$tg beta=frac{sin beta}{cos beta}=frac{3}{5}:frac{4}{5}=frac{3}{4}$
$ctg beta=frac{cos beta}{sin beta}=frac{4}{5}:frac{3}{5}=frac{4}{3}$