Tg a=1/3" tg B=-2 tg(a+B)=?

[latex]tg(a+b)= \frac{tga+tgb}{1-tga*tgb}= \frac{ \frac{1}{3}+(-2) }{1- \frac{1}{3}*(-2) } = \frac{ -\frac{5}{3} }{ -\frac{1}{3} }=5[/latex]