Tg3x+tg6 - tg9x=0 решить уравнение

По тождеству

tg (α + β) = (tgα + tgβ) / (1 - tgαtgβ)

tg3x + tg6x = tg * (3x + 6x) * (1 - tg3x*tg6x) = tg9x * (1 - tg6x*tg3x)

tg3x + tg6x - tg9x = 0

tg9x * (1 - tg3x*tg6x) - tg9x = 0

tg9x (1 - tg3x*tg6x - 1) = 0

tg9x*tg6x*tg3x = 0

tg9x = 0 или tg6xtg3x = 0

9x = πk или 6x = πk или 3x = πk, k∈Z

x = πk/9 или x = πk/6 или x = πk/3