What type of wave is described by this equation

[subopolois]

Homework Statement

x = (0.15 mm) cos (210x-120t)
what type of wave is described by this equation?

Longitudinal, transverse, angular frequency or both transverse and longitudinal

Homework Equations

NA

The Attempt at a Solution

there's really no calculation. I thinking its longitudinal because it is given as "x=". if it were transverse I am thinking it would be given as "y="
At the same time I am not even sure if I am right

 

[hackYou]

Some BS equation you got there.

 

[haruspex]

Taking the equation literally, with x on both sides, I don't recognise it as any of the usual wave equations. E.g. For a longitudinal wave, the x on the right would be the mean position of an oscillating segment, while the x on its left would be its displacement at time t; i.e. they should be two different variables.