Me again ! :surprised I have the following question and this time I really have no idea! 2 sinusoidal waves, identical except for their phase, travel in the same direction along a stretched string and interfere to produce a resultant wave given by: x(z,t) = 3Cos (20z-4t+0.82) Where x is in mm, z in metres and t in seconds a- What is the wavelength of the 2 original waves b- What is the phase difference between them c- What is their amplitude At the present I'm stuck on 'a' and may/may not be able to do b and c once I know how to work out 'a'. I can see how to add original waves, but how do I go about resolving the resultant wave? I guess it's similar to vector algebra, but mmmmm.... really don't know where to begin on this one. Any help would be very much appreciated.