1) tg(a + b) = (tg a + tg b)/(1 - tg a tg b)= 3/(1 =
- tg a tgb) (*) 2) Ctg a + Ctg b =1/tg a + 1/tg b = (tg b + tg
a)/tga tg b
Ctg a + Ctg b=(tg b + tg a)/tga tg b
4 = 3/ tg a. tgb
tg a-tg b = 3/4
3) Вернёмся к (")
tg(a + b) = 3:(1 - 3/4) = 3.4/1 = 12
