Four waves are described by the following expressions, where distances are measured in meters and times in seconds

I y = 0.12 cos(3x - 21t)
II y = 0.15 sin(6x + 42t)
III y = 0.13 cos(6x + 21t)
IV y = -0.23 sin(3x - 42t)
Which of these waves travel in the +x direction?
A)

I and II

B)

I and III

C)

II and IV

D)

I and IV

E)

II and III


D

Physics & Space Science

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