Math 125 Test 2 review Oct. 4, 2001
10 Problems 10 Points each

Topics
Chain Rule
- just a few "interesting" problems to differentiate.
Implicit Differentiation - including find slope and equation of tangent line at a point.
Curve Sketching without and with calculus

Related Rates
Here's how you get paid for Related Rate Problems 2 points each

Draw a picture and Label picture (if appropriate)
Describe all variables involved and state clearly what you are trying to find.
Find equation relating the variables
Differentiate w.r.t. time
Substitute in known values to solve for desired quantity


Max and Min Problems - Given Equations, find critical values and determine if they correspond to max or min points.

Optimization Problems - Given the situation, develop the equation, then find max or min required.
Here's how you get paid for Optimization Problems 2 points each

Draw a picture and Label picture (if appropriate)
Describe all variables involved and state clearly what you are trying to find.
Find equation(s) relating the variables, and write the objective variable (the one to be optimized) as a function of a single variable
Differentiate w.r.t. that single variable, find critical values, show your answer is max or min as desired.
Answer the question

Sample Problems

Chain Rule Differentiate:

1. y = sin2 4x
2. y = tan(cos 3x2)
3. y = 1 / (x2 - 3x)2
4. y = (x4(tan (3/x) )

Implicit Differentiation
1. Find dy / dx of sin3 (cos xy) = 5

2. Find dx / dy of x2 + 3x2 y - xy2 = 4


4. Find the equation of the tangent line to
(x+y)3 = x - y = 0 at the point (3, -1).

Curve Sketching: Find x & y intercepts, horizontal and vertical asymptotes and sketch

1. y = x(x-3)(x+4)2
2. y = (x-2)2(x+1)/(x+2)2 (x -1)2
3. x2 / (x2 + 1)

Related Rates
1. A rock is thrown into a pond, causing expanding rings with radius expanding at a constant rate of dr/dt = 6 m/s. How fast is the area of the of the circle increasing when the radius is 20 m ?

2. A winch on a motionless truck 6 feet above the ground is dragging a heavy load as indicated below. If the winch pulls the cable at a constant rate of 1.5 ft / second, how quickly is the load moving on the ground when it is 11 feet from the truck?

3. A triangle is expanding. Find the rate of change of area when the area is 30 square inches and the height is decreasing at a rate of 3 inches / second if the base remains fixed at 6 inches.

Optimization Problems
1. Profits in the Airdale business obeys the formula P = -A3 + 15A2 -48A - 6. How many should I raise?


2. A farmer is building a chicken pen in the shape of a rectangle and has 100 feet of fencing material. If one side is to be along side a raging river, (and chickens are smart enough to know they can't swim), what is the maximum area she can enclose?

3. What is the maximum volume of a closed cylinder with a surface area of 150 square inches?

4. A rectangular flat sheet of metal 18cm by 14 cm is to be formed into a box by cutting out equal sized squares from each corner. What is the maximum volume of this box?