Which property is represented by this numerical expression?
(6 + 11) + 23 = 23 + (6 + 11).

For a short time after a wave is created by wind , the height of the wave can be modeled using y= a sin 2pi(t) / t where a is the amplitude and t is the period of the wave in seconds. how many times over the first 5 seconds does the graph predict the wave to be 2 feet high?