AP Calculus BC

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麻烦大家帮偶解答几个AP难题吧。。
Q1:a point P is moving along the curve whose equation is y=√x. suppose that x is increasing at the rate of 4 units/s when x=3, how fast is the angle of inclination of the line segment from P to (2,0) changing at this instant?

Q2:a projectile is launched upwaed from ground level with an initial speed of 60m/s
# ^, L2 s/ n5 a! T* [1 H+ Q, d(a)how long does it take for the projectile to reach its highest point?
+ D0 C4 Q, u0 d  Z: C. V& X# V5 i(b)how high does the projectile go?
9 [" A' b; N9 h: P1 j! N% V4 v9 p(c)how long does the projectile go?
(d)what is the speed of the projectile when it hits the ground?
Use the results of these questions to make a conjecture about the relationship between the initial and final ground level and returns to ground level. Prove your conjecture.

Q3:a closed, cylindrical can is to have a volume of V cubic units. Show that the can of min surface area is achieved when the height is eaual to the diameter of the base.

Q4:a box-shaped wire frame consists of two identical wire squares whose vertices are connected by four straight wires of equal length. if the frame is to be made from a wire of length L. what should the dimensions be to obtain a box of greatest volume?