A sound wave produces an excess pressure P(t) (measured in units of millionths of atmospheric pressure) that repeats itself with a period of 2T = 1/110 seconds. The pressure is an even function of time, P(t) = P(−t), and is given by P(t) =
1, 0 < t < T/3
0, T/3 < t < 2T/3
-1, 2T/3 < t < T
Sketch the function P(t) in the range -T < t < T. Find the amplitudes and relative intensities of the first seven harmonics.