1. The problem statement, all variables and given/known data A spherical wave with a wavelength of 2.0 m is emitted from the origin. At one instant of time, the phase at r=4.0m is pi radians. At that instant, what is the phase at r=3.5m? 2. Relevant equations D(x,y,z,t)=Asin(kr-wt+phi) k=(2pi)/(lambda) w=(2pi)/T 3. The attempt at a solution (kr-wt+(phi))=phase constant D(x,y,z)=displacement, or here, radius A cancels and doesn't matter. 4/(pi)=3.5/x x=3.5(pi)/4 <---- which is wrong. So then I tried subtracting the equations... 4=Asin(pi) -3.5=-Asinx .5=Asin(pi)-Asinx .5=Asinx <---- Then I didn't know what to do with it. Help please?