Problem 6 The absolute value of velocity and the equation of the potential function lines in a two- dimensional velocity field (Fig. P3.21) are given by the expressions V = √4x²+4y² = x²-y²+C Evaluate both the left-hand side and the right-hand side of equation (3.16) to demonstrate the validity of Stokes's theorem of this irrotational flow. Rectangular area (2.1) Figure P3.21 (3.16)