решите уравнение:

7sin^2x+4sinxcosx - 3cos^2x=0

7sin^2x+4sinxcosx - 3cos^2x=0 / : cos^2x≠0

7tg^2x + 4tgx - 3 = 0

Пусть tgx=t, t ∈ (- беск; + беск.)

7t^2 + 4t - 3 = 0

t1 = - 1

t2 = 3/7

1) tgx = - 1 = = > x = - pi/4 + pik, k c Z

2) tgx = 3/7 = = > x = arctg (3/7) + pik, k c Z