cos5x = 0
5x = π/2 + kπ
x = π/2 × 1/5 + kπ/5 = π/10 + kπ/5
___________
2cos(2x - 1) = 0
cos(2x - 1) = 0
2x - 1 = π/2 + kπ
2x = π/2 + 1 + kπ
x = π/2 × 1/2 + 1/2 + kπ/2 = π/4 + 1/2 + kπ/2
___________
sin3x = 0
3x = kπ
x = kπ/3
___________
cos4x = 1
4x = 2kπ
x = 2kπ/4 = kπ/2
