3 ctd^2(3П/2+х/3)-2 tg x\3=1
Решение: 3tg^2x/3-2tgx/3-1=0 tgx/3=t 3t^2-2t-1=0 t=1 tgx/3=1 x/3=П/4+Пk x=3П/4+3пk t=-1/3 tgx/3=-1/3 x/3=-arctg1/3+Пk x=-3arctg1/3+3Пk.