Question

найдите sin, tg, ctg если cos =2/3

Answer 1

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