The function L(t) = 12 + 3.4 sin( 2/365 t) models the length of a day from

The function L(t) = 12 + 3.4 sin( 2π/365 t) models the length of a day from sunrise to sunset in Sapporo, Japan, where t is the day in the year after the spring equinox on March 21. Determine L'(t), and use it to calculate the rate that the length of the days are changing on December 1, January 1, and February 1. Discuss what the results say about the changing day length in the late fall and winter in Sapporo.