Long description

This figure shows the first partial derivatives of u and v with respect to x and y, shown in a two by two grid. Top left: partial derivative of u of x and y with respect to x equals two times x. Bottom left: partial derivative of u of x and y with respect to y equals two times y. Top right: partial derivative of v of x and y with respect to x equals two. Bottom right: partial derivative of v of x and y with respect to y equals four. The partial derivatives of u with respect to x and that of v with respect to y are grouped in a bubble, as are the partial derivatives of u with respect to y and that of v with respect to x.