Draw a circle in the xy plane. At a few representative points draw the vector v tangent to the circle, pointing in the clockwise direction. By comparing adjacent vectors, determine the *sign* of ∂vx/∂y and ∂vy/∂x. According to Eq. 1.41, then, what is the direction of ∇×v? Explain how this example illustrates the geometrical interpretation of the curl.