Question

Если tg x=1, tg(x-y)=3, то tg y равен ..

Answer 1

$tgx=1$
$tg(x-y)=3$
$tg(x-y)= \frac{tgx-tgy}{1+tgx*tgy}$
$\frac{1-tgy}{1+tgy} =3$
$tgy \neq -1$
$1-tgy=3*(1+tgy)$
$1-tgy=3+3*tgy$
$4*tgy=-2$
$tgy=-0.5$