# Homework Help: Interpreting this wave funtion

1. Oct 23, 2008

### RJS

1. The problem statement, all variables and given/known data

find Amplitude, wavelength and velocity of wave from the two combined waves.

there are two waves here, combined into one, show each wave function: y1(x,t) and y2(x,t).

2. Relevant equations

ok, i can fully manipulate the wave function when it's in it's basic form of y(x,t)=Acos(kx-wt+phi) but i must be missing something here. is the problem in a form that can be worked or must it be reworked with a trig function? it's all being multiplied so i'm not sure how to get it into the (kx-wt) format.

any help would be appreciated.

thanks.

3. The attempt at a solution

because they are two waves in this equation Amplitude is (4.8mm/2)=2.4mm... correct?

wave length can be found using kx= [2(pi)x]/(lambda) and velocity will be found using wt=2(pi)tf to find frequency and then v=(lambda)(frequency)

my question is do i need to change the equation? or can i just use it as is?

I don't have the answer to this question, so if you can point me in the right direction?

Last edited: Oct 23, 2008
2. Oct 23, 2008

### Redbelly98

Staff Emeritus
You're correct on amplitude, wavelength, frequency and velocity.

In addition, yes you will need to change the equation, since it asks explicitly to "show each wave function: y1(x,t) and y2(x,t)."

If you can figure out how to express
sin(a)cos(b)
in terms of
sin(a+b), sin(a-b), cos(a+b), and/or cos(a-b)
using trig-addition identities, then it is solvable.