Tthis is a sinusoidal function and the following information is given, the lenght of a day was 12 hours on may 1st
The length of a day kept going up until it reached its max at 15 hours and 30 mins. It then continued going down until its minimum at 8 hours and 30mins. It finally went back up to 12 hours on may 1st. What is the function rule?