# Active Reading Solution: The Standing Wave Equation

- Plugging in
*t=T/4* turns this equation into *y(x) = A sin(2px/l)*. At that instant the string looks like a sine wave with amplitude *A* and wavelength l. (At other times the wave has different amplitudes, but always the same wavelength.)

- Plugging in
*x=l/8* turns this equation into *y(t) = sin(2pt/T)*. That particular point on the string is oscillating with amplitude is and period *T*. (At other locations the wave has different amplitudes, but always the same period.)

And here comes a great video that Gary made!