As you have previously seen, the number of minutes S between sunrise and sunset in any one location for a particular day of
the year can be modeled by a variation of the basic sine or
cosine function. One approximate model for the number
of minutes between sunrise and sunset in Washington, D. C.,
is S(d)= 180 sin (0.0172d - 1.376) + 720, where d is the
day of the year with January 1 as day 1.