The percentage of the lighted surface of the Moon that is visible from Earth can be modeled with a sinusoid. Assume that tonight the Moon is full (100%) and in 14 days it will be a new moon (0%).
a. Define variables and find a sinusoidal function that models this situation.
b. What percentage will be visible 23 days after the full moon?
c. What is the first day after a full moon that shows less than 75% of the lit surface?