Wave equation 2D with only 1 output

How does one type the wave equation into the equation editer of FEATool for MATLAB and with only 1 dependent variable u in 2D space?

It is currently not possible to define and solve equations with 2nd order (or more) time derivatives in FEATool. You have to transform the problem as shown in the tutorial:

https://featool.com/doc/Classic_PDE_01c_wave_equation1

Oh ok thanks!