Solution
By definition, div⟨sin(xy),cos(xy),ez⟩=∇⋅⟨sin(xy),cos(xy),ez⟩, or, equivalently, div⟨sin(xy),cos(xy),ez⟩=⟨∂x∂,∂y∂,∂z∂⟩⋅⟨sin(xy),cos(xy),ez⟩, where ⋅ is the dot product operator.
Thus, div⟨sin(xy),cos(xy),ez⟩=∂x∂(sin(xy))+∂y∂(cos(xy))+∂z∂(ez).
Find the partial derivative of component 1 with respect to x: ∂x∂(sin(xy))=ycos(xy) (for steps, see derivative calculator).
Find the partial derivative of component 2 with respect to y: ∂y∂(cos(xy))=−xsin(xy) (for steps, see derivative calculator).
Find the partial derivative of component 3 with respect to z: ∂z∂(ez)=ez (for steps, see derivative calculator).
Now, just sum up the above expressions to get the divergence: div⟨sin(xy),cos(xy),ez⟩=−xsin(xy)+ycos(xy)+ez.