Question

Найдите sin, tg, ctg если cos =2/3

Answer 1

$sin= \sqrt{1-cos^2}= \sqrt{1-4/9}= \sqrt{5/9} = \sqrt{5} /3$
$tg=sin/cos= \frac{2*3}{3 \sqrt{5} } = \frac{2}{ \sqrt{5} } = \frac{2 \sqrt{5} }{5}$
$ctg=1/tg= \sqrt{5} /2$