2 cos ^2 + 5 cos x =3

Question

2 cos ^2 + 5 cos x =3

Answer 1

1) заменим cosx = a2a² + 5a - 3 =0-5±√25+24 /4 = a1 = -3, а2 = 1/2а1 не подходит.cosx = 1/2x = ±π/3 + 2πn