Chapters 7 - 9
1. Evaluate the following integrals by hand. Show all steps. Use your calculator to check your
∫ x sin(2 x) dx
4x + 3
(d) ∫ 2
x + 3x + 2
ln( x) dx
arctan( x) dx
3x 2 + x + 3
x3 + x
2. Simpson’s rule uses parabolas to approximate integrals. It is not surprising that it gives the
exact result when integrating 2nd degree polynomials. Remarkably, it also gives the exact answer
when integrating polynomials of degree three.
x 3 dx .
(b) Use S 4 , Simpson’s Rule to approximate the integral in (a).
(c) Use T4 , the Trapezoidal Rule to approximate the integral in (a).
3. Assume that f is a function defined on the interval [a , b] and f ′ < 0 and f ′′ > 0 on [a , b].
Rank the following from least to greatest: L n , R n , M n , T n , and ∫ f ( x )dx , where L n , R n , M n
, T n are the left, right, midpoint, and trapezoidal rules respectively using n subintervals. Draw
figures to justify your answer.
4. Evaluate the following improper integrals by hand. Show all steps. Sketch the curve and the
region represented by the integral. Use your calculator to check your answers:
ln( x) dx .
5. A swimming pool is 20 ft wide and 40 ft long and its bottom is an inclined plane. The
shallow end has a depth of 3 ft and the deep end 9 ft. If the pool is full of water, find the
hydrostatic force on one of the trapezoidal sides.
6. Find the centroid ( x , y ) for the right triangle with vertices at ( 0 , 0 ), ( a , 0 ), and ( a , b ).
Estimate ( x , y ) first.
7. Find the solution to the initial value problem
dy x + sin( x )
y(0) = 2
Answer the questions below for the differential equation y ′ = 3 − y .
Draw the direction field for the differential equation.
Use your direction field to draw the solution going through the origin.
If y (0) = 0 , use two steps of Euler’s method to approximate y (.2) .
9. If y (t ) is the temperature of an object in a room of constant temperature R , then the
differential equation for Newton's Law of Cooling is y ′(t ) = k ( y (t ) − R) .
a) Explain what this differential equation means in plain English.
b) A can of soda has temperature 40 o F when taken from a cooler and placed in a room of
72 o F . Five minutes later the soda is 56 o F . When will the temperature of the soda be 64 o F ?
10. A simple series circuit consists of a 25 ohm resistor, a .01 farad capacitor and a constant
EMF E (t ) = 50 volts. If the initial charge on the capacitor is 4 coulombs, set up and solve an
initial value problem to determine the charge Q(t ) and current I (t ) for t > 0 .
11. Use the product rule to prove the integration by parts formula (eq #1 section 7.1).