Consider the functions cos(x), cos(0.1x), and cos(3pix).
a. Over what interval of x will x vary by 2pi?
b. Over what interval of x will 0.1x vary by 2pi?
c. Over what interval of x will 3pix vary by 2pi?
(a) 2π
(b) 2π/0.1
(c) 2π/3π
cos(kx) has a period of 2π/k