How do I write $sin(pi*x)*sin(pi*y)?

I tried to solve on and on the boundary.

I get error when I write . Can anyone help in the following code?

model = createpde;
g = geometryFromEdges(model,@squareg);
pdegplot(model)
pdegplot(model,'EdgeLabels','on'); 
axis equal
applyBoundaryCondition(model,'dirichlet','Edge',1:model.Geometry.NumEdges,'u',0);
specifyCoefficients(model,'m',0,'d',0,'c',1,'a',0,'f',sin(pi*x)*sin(pi*x));