a) Explain the meaning of the word "equinox" and describe what happens on that day

according to the above formula.

(b) What is the length of the shortest and the longest day and when do these occur accord-

ing to this formula?

(c) How long is one complete cycle in this expression?

(d) Sketch l(t) as a function of t

(e) Find the average day-length over the month immediately following the equinox.

(f) Find the average day length over the whole year. Explain your result with a simple

geometric or intuitive argument.

Exercise 4.26 The length of time from sunrise to sunset (in hours) & days after the Spring Equinox is given by 1(4) = 12 + 4 sin 182