15-14-13-12-11 -10 -9 -8 -7-6-5-4 2 B -2 -1 8 9 10 11 12 13 The curve above is the graph of a sinusoidal function. It goes through the points (-13, 0) and (1,0) Find a sinusoidal function that matches the given graph. If needed, you can enter -3.1416... as 'pi' in your answer, otherwise use at least 3 decimal digits. f(r).