An object with weight W is dragged along a horizontal plane by a force acting along a rope attached to the object. If the rope makes an angle t with the plane, then the magnitude of the force is \displaystyle F=\frac{\mu W}{\mu \sin{t}+\cos{t}} , where \mu is a constant called the coefficient of friction. Let W=25 lb and \mu=0.5 .

(a) Find the rate of change of F with respect to

(b) When is this rate of change equal to zero? Round your answer to the nearest hundredth.

You can earn partial credit on this problem.