Question

tgA=?
tgB=2
tg(A+B)=-1

Answer 1

$tg(a+b)=\frac{tg a+tg b}{1-tg a\cdot tg b};\ -1=\frac{tg a+2}{1-2tg a};\ -1+2tg a=tg a+2;\ tg a=3$