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## Homework Statement

I am really confused with the equations.

For travelling waves, in some places they write y = A cos (kx - wt) for waves travelling in the positive x-direction. Then some write y = A sin (wt - kx) for waves travelling in the positive x-direction while others write

y = - A sin (wt - kx) or y = A sin (kx - wt) all for waves travelling in the positive x - direction.

Then for standing waves, in the example in our book, they used the case of an incident wave at a fixed end causing an inverted reflection so they used y = A cos (kx - wt) for positive and y = - A cos (kx + wt) for the negative and inverted reflected wave to get a standing wave equation of y = 2 A sin kx sin wt whereas in other places they used one of the million above mentioned sine functions and got an answer of y = 2 A sin kx cos wt.

So confused as to what is right! They want us to use the sine functions. Please help, thank you.

## Homework Equations

y = A cos (kx - wt)

y = A sin (wt - kx)

y = - A sin (wt - kx) or y = A sin (kx - wt)

y = 2 A sin kx sin wt

y = 2 A sin kx cos wt

## The Attempt at a Solution

As mentioned above.