Verified answer

Ответ:

1)

[tex] \cos(4x) \cos(2x) - \sin(4x) \sin(2x) \\ \cos(4x + 2x) \\ \cos(6) [/tex]

2)

[tex] \sin(2y) \cos(8y) + \cos(2y) \sin(8y) \\ \sin(2y + 8y) \\ \sin(10y) [/tex]