Calculating Energy of Two Transverse Waves

[bon]

Homework Statement

Two transverse waves are on the same piece of string. The first has non-zero displacement only for kx + wt between pi and 2pi when it is equal to Asin(kx+wt). The second has y=Asin(kx-wt) for kx-wt between -2pi and -pi and is zero otherwise. Calculate the energy of the waves when t=0.

Homework Equations

The Attempt at a Solution

Ok so I've sketched the waves...they look like two wavefront (one above the axis, one below) approaching each other..

I'm just not sure how to find the energy..

 

[vela]

This page has a good discussion about the energy of a wave on a string.

http://galileo.phys.virginia.edu/classes/152.mf1i.spring02/AnalyzingWaves.htm