Sales of snowmobiles are seasonal. Supposed sales in Camrose, Alberta are approximately by S=200+200cos[pi/6(t+2)], where t is time in months with t=0 corresponding to January. For what months are sales equal to 0.

Answer 1

when cos(pi/6 (t+2)) = -1
That is, where

pi/6 (t+2) = pi