Решить уравнение  3sin²x+7cosx-3=0

3(sinx)^2 +7cosx-3=0 3(1-(cosx)^2)+7cosx-3=0 3-3(cosx)^2 +7cosx-3=0 3(cosx)^2-7cosx=0 cosx(3cosx-7)=0 cosx=0                                   или                       3cosx-7=0 x=П/2+Пn, n принадлежит Z                                3cosx=7                                                                             cosx=7/3                                                                              корней нет, т.к.                                                                             |cosx|<=1