Cual sera el resultado?

Jessica and Matthew are running toward the point P along the straight paths that make a fixed angle of 0 (Figure 1). Suppose that Matthew runs with velocity v. (m/s) and Jessica with velocity vt (m/s). Let f(x, y) be the distance from Matthew to Jessica when Matthew is a meters from P and Jessica is y meters from P. A FIGURE 1 . Show that f(x, y) = vx2 + y2 - 2xy cos 0. . Assume that 8 = 1/3. Use the Chain Rule to determine the rate at which the distance between Matthew and Jessica is changing when x - 30, y = 12, va = 4 m/s, and v. = 5 m/s