Question about Nodes of a Standing Wave

(See attached file for full problem description)

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Nodes of a Standing Wave (Cosine)
Learning Goal: To understand the concept of nodes of a standing wave.
The nodes of a standing wave are points where the displacement of the wave is zero at all times. Nodes are important for matching boundary conditions, for example that the point at which a string is tied to a support has zero displacement at all times (i.e., the point of attachment does not move).
Consider a standing wave, where represents the transverse displacement of a string that extends along the x direction. Here is a common mathematical form for such a wave:

where is the maximum transverse displacement of the string (the amplitude of the wave), which is assumed to be nonzero, is the wavenumber, is the angular frequency of the wave, and is time.

Part A
Which one of the following statements about wave is correct?
Which one of the following statements about wave is correct?

This wave is traveling toward

This wave is traveling toward .

This wave is oscillating but not traveling.

This wave is traveling but not oscillating.

Part B
At time , what is the displacement of the string ?
Express your answer in terms of , , and other previously introduced quantities.

= __________________

Part C
What is the displacement of the string as a function of at time , where is the period of oscillation of the string?
Express the displacement in terms of , , and only. That is, evaluate and substitute it in the equation for .

= __________________

Part D
At which three points , , and closest to but with will the displacement of the string be zero for all times? These are the first three nodal points.
Express the first three nonzero nodal points as multiples of the wavelength , using constants like . List the factors that multiply in increasing order, separated by commas.

, , = ___________________
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