Posted by Nurcan on .
A model for the length of daylight (in hours) in Philadelphia on the t th day of the year is
L(t)= 12+2.8 sin[2pi/365(t80)]
Use this model to compare how the number of hours of daylight is increasing in Philadelphia on March 21 and May 21. (Assume there are 365 days in a year. Round your answers to four decimal places.
March 21 L'(t)= ?
May 21 L'(t)=?
I found;
L'(t)=2.8cos(2pi/365(t80))(2pi/365)

Calc..Help Please 
MathMate,
I get the same derivative.
You can post your numerical answer for a check if you wish.