Question

1) cos7x-cos3x=0

2) tan4x-tan6x=0

Answer 1

1) cos4x = 0
4x = π/2 + πn, n€Z
x = π/8 + πn/4, n€Z

2) tg(-2x) = 0
-2x = π + πn, n€Z
x = -π/2 - πn/2, n€Z