A-alfa,b-beta ------------------ Вычислите tg (a+b) u tg(a-b), если tga=1/3, tgb=1/5.

[latex]tg(alpha+eta)=frac{tgalpha+tgeta}{1-tgalpha*tgeta}=frac{frac{1}{3}+frac{1}{5}}{1-frac{1}{3}*frac{1}{5}}=frac{frac{8}{15}}{frac{14}{15}}=frac{8}{14}=frac{4}{7}\\\tg(alpha-eta)=frac{tgalpha-tgeta}{1+tgalpha*tgeta}=frac{frac{1}{3}-frac{1}{5}}{1+frac{1}{3}*frac{1}{5}}=frac{frac{2}{15}}{frac{16}{15}}=frac{2}{16}=frac{1}{8}[/latex]