| |
Hints for Online HW (2nd number refers to problem from book in §8.1)
- =8.1.9.
Note that e-x = 1⁄ ex.
So the denumerator of the fraction
(1)
/
[e-x + ex ]
is really a fraction itself.
So we algebraically clean up this fraction divided by a fraction as:
(1)
/
[e-x + ex ]
=
(1)
/
[
(1
/
ex)+ ex ]
=
(1)
/
[
(1
/
ex)+
(ex ex
/
ex )]
=
(1)
/
[
(1+ e2x)
/
(ex)]
=
(ex)
/
[1+ e2x].
Hopefully this helps motivate a MML-hint
that to simplify the expression
such as
(1)⁄ [e-x + ex],
one just multiplies the expression by
(ex)⁄ [ex],
which is just the number 1, cleaverly written.
- =8.1.11. Do a u-du sub. to express the integral as an integral from page 2 of your
blue sheet.
Do not forget that, when doing definite integral, if you have a dx
then your limits of integration must be as x varies (so from
x= to x= ) while if you have a du
then your limits of integration must be as u varies.
- =8.1.36. Complete the square under the square root sign and then
do a u-du sub. to express the integral as an integral from page 2 of your
blue sheet.
- =8.1.3. Preview of to-come §8.3 (Trig Integrals). Using basic trig identities, rewrite the integral as a sum
of integrals with each one do-able, perhaps after a u-du substitutions,
using page 2 of your blue sheet.
- =8.1.5. Preview of to-come §8.4 (Trig Sub). Rewrite the integral as a
sum of two integrals where each integral, after the proper u-du substitutions,
is do-able using page 2 of your blue sheet.
- =8.1.21. Preview of to-come §8.5 (Partial Fractions). The integrand is
a rational function, i.e., a polynomial y=p(t) divided by another
polyomial y=q(t). We will learn that if you want to
integrate such a rational function
[p(t)]⁄[q(t)] and we do NOT have
"strictly bigger bottoms" (i.e., the degree of q is NOT stricly
bigger than the degree of p), then first rewrite the rational
function by doing long division of polynomial. In the given
problem, since the degree of the bottom q is 2
while the degree of the top p is 3,
we do NOT have "strictly bigger bottoms". So do long division to
rewrite the given rational function as a sum of fucntions,
each of whose integral, after the proper u-du substitutions, is do-able
using page 2 of your blue sheet.
- =8.1.41. Express the area as an integral (see §5.6).
- =8.1.43. Express the arc length as an integral (see §6.3).
| |
Below is a u-du sub. review from another book.
Stewart (6th ed, ET), §5.5.
| | need more practice? |
Having troubles or want more practice? Work through some more of the above 88 exercises.
This is a good source and you have the solutions.
| | need more practice? |
Want or need even more practice with u-du substitution? Try these
23(=30-7) u-du substitution problem (answers included).
Anton (8th ed, ET) |
8.2 Parts | | |
Online HW | | |
You do not need to know tabular integration, which basically is a
method (which students tend to misuse) to accomplish something that
can easily be done with high-school algebra.
|
|
|
Parts is just one (of many) techniques (of integration) we will learn
in this chapter.
Which technique to use on a given integral -
a good ansatz is a techique already taught.
Thus far, in this second section in the chapter on Techniques of Integration,
we have only 2 techniques in our tool box: substitution and parts.
As we learn more techniques,
it becomes tricker to answer the question: which technique to use?
The answer lies in true understanding and pattern recognition (useful skills).
So take out a sheet of paper and do the following.
- Recall the 5 KEY IDEAS from Parts taught in class (also on
the
Integration Basics handout). Write out each Key Idea, leaving space between the key ideas.
- Under each Key Idea, list out the specific integrals from the homework
assignment that used that Key Idea.
(e.g., Under "Bring to the other side method", write
"23. ∫ e2x cos 3x dx").
- Go back and look for patterns/hints on why and how parts works.
- Did this help? If not - do more problems.
| | need more practice? |
Try these
exercises.
Answers
to the odd problems. Give the exercises an honest shot before peeking at the
solutions
to all of them. Stewart (6th ed, ET)
|
8.1&8.2
|
|
|
A Sample Recitation Quiz
over Sections 8.1&8.2, along with the solution.
Would you be able to work this quiz at the end of a recitation over
Sections 8.1&8.2, in 10 minutes, without your books/notes?
|
8.3 trig integrals |
|
  |
Online HW
| | need more practice? |
Try these
exercises.
Answers
to the odd problems. Give the exercises an honest shot before peeking at the
solutions to all of them.
Stewart (6th ed, ET)
|
8.4 trig substitution |
|
  |
Online HW
| | |
Also do
these (click here)
two problems (hint: complete the square)
|
| need more practice? |
Try these
exercises.
Answers
to the odd problems. Give the exercises an honest shot before peeking at the
solutions to all of them.
Stewart (6th ed, ET)
|
8.5 partial fractions |
|
  |
Online HW
|
| need more practice? |
Try these
exercises.
Answers
to the odd problems. Give the exercises an honest shot before peeking at the
solutions to all of them.
Stewart (6th ed, ET)
|
Review of 8.1-8.5 | | |
Time to test your pattern recognition skills (valuable skill no matter where your
academic pursuit leads you).
For each of Sections 8.1 through 8.5, look over the section's examples with an eye on
what properties are shared by integrals that can be solved using that section's technique.
|
81 Integrals | |
Do these
81 Integrals
-
You should work 10 integrals a day, 7 days a week,
until you finish all these integrals.
-
Answers
to the odd problems.
- Give the exercises an honest shot before peeking at the
solutions to all of them.
Stewart (6th ed, ET)
|
100 Integrals
| need more practice? |
Try these
100 Integrals
- Omit numbers: 17, 51, 72, 74, 96, 97, 101-105, 112, 113.
- The answers to the odd number problems.
- Prof. Girardi's handwritten
solutions to the circled problems: 1, 3, 7, 23, 26, 35, 36, 47, 50, 71.
- 28 pages of hints/answers/solutionsfor all
(#1-119) the problems.
Edwards&Penny (3rd ed)
|
8.6 | | | We are not covering this section on Tables and CAS's.
| 8.7 | | | No Online HW. HW is as given in a Maple Lab. |
8.8 Improper Integrals
without comparison tests (DCT/LTC)
and
with comparison tests (DCT/LTC)
|
For §8.8 OFF-LINE homework, use the below source (note, not our textbook).
- homework problems
- answers to odd
- solutions to all
(use responsiblity)
For problems within 5-40, for a divergent improper integral,
explain why it diverges (eg., dvg to ∞, dvg to -∞, dvg but not to ±∞).
Remarks on the above solutions.
- The solutions often refer to Equation 2. This is our book's Example 3 on page 507,
which is
∫1∞
1⁄xp dx
is convergent if p>1 and divergent if p ≦ 1.
We did this example in class.
-
There are different ways on integral can be improper.
Be able to explain, in an English sentence and not by a number (1,2,3,4,5,6,I,orII), why an integral is improper.
For the purpose of learning, I divided the ways into numbers 1-6 on the
Improper Integrals
handout in class. Just as our book does (see the definitions on pages 505&508),
this homework source calls ways 1-3 of Type I
and ways 4-6 of Type II.
|
ON-LINE HW | | Two Online HW sets. One set without, and one set with, the DCT/LCT.
Take notice of the number of attempts per problem for each set.
OFF-LINE HW with comparison tests (DCT/LCT) |
| For the above (not the textbook) source of problems, use
the specified comparison test (DCT or LCT) to determine if the integral is conervgent or divergent.
- use DCT for 49, 50, 51, 52.
- use LCT for the following slight variants of 49, 50, 51.
The variants are chosen so that one compares the integrand to
the same g as in the original problem but, in the variant, the DCT does not
easily work (why? check which way the bound easily goes) but the LCT easily works.
Remark/Hint.
49 but change
(x)⁄(x3 + 1) to
(x)⁄(x3 ‒ 1) .
Ans: convergent.
50 but change
(2 + e-x)⁄(x) to
(2 ‒ e-x)⁄(x). Ans: divergent.
51 but change
(x+1)⁄
√x4
‒x to
(x+1)⁄
√x4
+x. Ans: divergent. |
| For the above (not the textbook) source of problems: 71, 72, 73
(an introducation to the Laplace transform,
which is used in many branches of the sciences and engineering)
|
| need more practice?
| For more practice without the comparison tests,
from the above (not the textbook) source of problems,
a good selection is: 1, 2, 5, 7(dvg to ∞), 13,
15(dvg but not to ±∞), 19, 23, 27(dvg to ∞) , 31(dvg to ∞), 41, 59, 61, 71. |
Then Exam 1 over 8.1-8.5, 8.8. |
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