Найдите tg a, если 3 sin^2 a + 8 cos^2 a=4

3 sin^2 a + 8 cos^2 a = 4;

3 sin^2 a + 8cos^2 a = 4 (sin^2 a + cos^2 a);

3sin^2 a + 8cos^2 = 4 sin^2 a + 4 cos^2 a;

sin^2 a = 4 cos^2 a; / : cos^2 a ≠ 0;

tg^2 a = 4;

tga = 2

tg a = - 2