Let's say for example this pizza had 6 slices to start with. Two-thirds of this is (2/3)*12 = 4 slices. So you have 4 slices left over from yesterday. Then let's say you hand one slice to each of your four friends. Each friend would have 1/6 of the original pizza.
The given equation is a wave function. When plotted, the graph is shown in the attached picture. However, the unit is in degrees instead of radians. A unit of π is equivalent to 180°. This plot could determine one variable if the other is given.
