# Help with sinusoidal function rule

• June 14th 2012, 05:09 PM
danny88
Help with sinusoidal function rule
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?

Thanks
• June 15th 2012, 12:39 AM
richard1234
Re: Help with sinusoidal function rule
Let May 1 correspond with $x = 0$ and $x = 365$. The "amplitude" is 3.5 hours. Hence our equation could look something like

$f(x) = 12 + 3.5 \sin {\frac{x}{365}}$