f1[x_,y_] = Sin[x]Sinh[π-y];

D[f1[x,y],x]

D[D[f1[x,y],x],x]

D[f1[x,y],y]

D[D[f1[x,y],y],y]

Simplify[D[D[f1[x,y],x],x]+D[D[f1[x,y],y],y]]

Grad[f1[x,y],{x,y}]

Grad[Grad[f1[x,y],{x,y}],{x,y}]

MatrixForm[%]

Tr[%%]

Plot3D[f1[x,y],{x,-π,π},{y,-π,π},Mesh->False,PlotStyle->Opacity[0.3],PlotRange->All]

f2[x_,y_] = Sinh[2x]Sin[2y];

D[f2[x,y],x]

D[D[f2[x,y],x],x]

D[f2[x,y],y]

D[D[f2[x,y],y],y]

Simplify[D[D[f2[x,y],x],x]+D[D[f2[x,y],y],y]]

Grad[f2[x,y],{x,y}]

Grad[Grad[f2[x,y],{x,y}],{x,y}]

MatrixForm[%]

Tr[%%]

Plot3D[f2[x,y],{x,-π,π},{y,-π,π},Mesh->False,PlotStyle->Opacity[0.3],PlotRange->All]