Решите уравнение cos^2x-3sinxcosx=-1

Вроде так)

cos^2x-3sinxcosx=-1

cos^2x-3sincos+sin^2+cos^2=0

2cos^2+sin^2-3sincos=0

2+tg^2-3tg=0

D=1

X1,2= 2;1

tgx=2                                         tgx=1

x=arctg2+pk                             x=p/4+pk

x=p-arctg2+pk