# Another Trig question (sine wave)

During a strong wind, a tall building, such as the CN Tower, can sway back and forth as much as 100 cm, with a period of 10s.

b) Write an equation for this function, in the form y = a sin kx

2Pi / k = 10
10k = 2Pi
k = Pi/5

y = 100sin(Pi/5)x

Now my question is regarding the wording of the question. It says that it can sway back and forth as much as 100 cm but does not state if that is the diameter or radius. Am I correct in thinking it is referring to the radius?

Or would the correct answer be: y = 50sin(Pi/5)x because it swings 50 cm each way? Sorry to ask such a stupid question I'm just not 100% sure what it is asking.

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I'm pretty sure they mean 100cm is the 'radius' (properly called the amplitude of vibration).

HallsofIvy