Решите:3-42sin 21x cos 21x<3

Question

Решите:3-42sin 21x cos 21x<3

Answer 1

42Sin21xCos21x > 0
21Sin42x > 0
Sin42x > 0
0 + 2πn < 42x < π + 2πn , n ЄZ<br>πn/21 < x < π/42 + πn/21 , n ЄZ