imfm.qxd 9/15/05 12:06 PM Page i
,imfm.qxd 9/15/05 12:06 PM Page ii
INSTRUCTOR’S
MANUAL FOR
ADVANCED
ENGINEERING
MATHEMATICS
NINTH EDITION
ERWIN KREYSZIG
Professor of Mathematics
Ohio State University
Columbus, Ohio
JOHN WILEY & SONS, INC.
,im01.qxd 9/21/05 10:17 AM Page 1
Part A. ORDINARY DIFFERENTIAL
EQUATIONS (ODEs)
CHAPTER 1 First-Order ODEs
Major Changes
There is more material on modeling in the text as well as in the problem set.
Some additions on population dynamics appear in Sec. 1.5.
Electric circuits are shifted to Chap. 2, where second-order ODEs will be available.
This avoids repetitions that are unnecessary and practically irrelevant.
Team Projects, CAS Projects, and CAS Experiments are included in most problem sets.
SECTION 1.1. Basic Concepts. Modeling, page 2
Purpose. To give the students a first impression what an ODE is and what we mean by
solving it.
Background Material. For the whole chapter we need integration formulas and
techniques, which the student should review.
General Comments
This section should be covered relatively rapidly to get quickly to the actual solution
methods in the next sections.
Equations (1)–(3) are just examples, not for solution, but the student will see that
solutions of (1) and (2) can be found by calculus, and a solution y = ex of (3) by inspection.
Problem Set 1.1 will help the student with the tasks of
Solving y' = ƒ(x) by calculus
Finding particular solutions from given general solutions
Setting up an ODE for a given function as solution
Gaining a first experience in modeling, by doing one or two problems
Gaining a first impression of the importance of ODEs
without wasting time on matters that can be done much faster, once systematic methods
are available.
Comment on “General Solution” and “Singular Solution”
Usage of the term “general solution” is not uniform in the literature. Some books use the
term to mean a solution that includes all solutions, that is, both the particular and the
singular ones. We do not adopt this definition for two reasons. First, it is frequently quite
difficult to prove that a formula includes all solutions; hence, this definition of a general
solution is rather useless in practice. Second, linear differential equations (satisfying rather
general conditions on the coefficients) have no singular solutions (as mentioned in the
text), so that for these equations a general solution as defined does include all solutions.
For the latter reason, some books use the term “general solution” for linear equations only;
but this seems very unfortunate.
1
, im01.qxd 9/21/05 10:17 AM Page 2
2 Instructor’s Manual
SOLUTIONS TO PROBLEM SET 1.1, page 8
2. y = —e—3x/3 + c 4. y = (sinh 4x)/4 + c
6. Second order. 8. First order.
10. y = ce0.5x, y(2) = ce = 2, c = 2/e, y = (2/e)e0.5x = 0.736e0.5x
12. y = cex + x + 1, y(0) = c + 1 = 3, c = 2, y = 2ex + x + 1
14. y = c sec x, y(0) = c/cos 0 = c = _1π, y = _1π sec x
2 2
16. Substitution of y = cx — c2 into the ODE gives
y'2 — xy' + y = c2 — xc + (cx — c2) = 0.
Similarly,
y = _1x2, y' = _1x, thus _1x2 — x(_1x) + _1x2 = 0.
4 2 4 2 4
18. In Prob. 17 the constants of integration were set to zero. Here, by two integrations,
y” = g, v = y' = gt + c , 1 y = _1gt2 + c t + c ,
2 1 2 y(0) = c = y ,
2 0
and, furthermore,
v(0) = c1 = v0, hence y = _21gt2 + v0 t + y0,
as claimed. Times of fall are 4.5 and 6.4 sec, from t = √1¯ 00/4.9̄ and √2¯
00/4.9̄.
20. y' = ky. Solution y = y0 ekx, where y0 is the pressure at sea level x = 0. Now
y(18000) = y0 ek·18000 = _12y0 (given). From this,
ek·18000 = _1, y(36000) = y ek·2·18000 = y (ek·18000)2 = y (_1)2 = _1y .
2 0 0 0 2 4 0
22. For 1 year and annual, daily, and continuous compounding we obtain the values
ya(1) = 1060.00, yd(1) = 1000(1 + 0.06/365)365 = 1061.83,
yc(1) = 1000e0.06 = 1061.84,
respectively. Similarly for 5 years,
ya(5) = 1000 · 1.065 = 1338.23, yd(5) = 1000(1 + 0.06/365)365·5 = 1349.83,
yc(5) = 1000e0.06·5 = 1349.86.
We see that the difference between daily compounding and continuous compounding
is very small.
The ODE for continuous compounding is yc' = ryc.
SECTION 1.2. Geometric Meaning of y' = ƒ(x, y). Direction Fields, page 9
Purpose. To give the student a feel for the nature of ODEs and the general behavior of
fields of solutions. This amounts to a conceptual clarification before entering into formal
manipulations of solution methods, the latter being restricted to relatively small—albeit
important—classes of ODEs. This approach is becoming increasingly important, especially
because of the graphical power of computer software. It is the analog of conceptual
studies of the derivative and integral in calculus as opposed to formal techniques of
differentiation and integration.
Comment on Isoclines
These could be omitted because students sometimes confuse them with solutions. In the
computer approach to direction fields they no longer play a role.
,imfm.qxd 9/15/05 12:06 PM Page ii
INSTRUCTOR’S
MANUAL FOR
ADVANCED
ENGINEERING
MATHEMATICS
NINTH EDITION
ERWIN KREYSZIG
Professor of Mathematics
Ohio State University
Columbus, Ohio
JOHN WILEY & SONS, INC.
,im01.qxd 9/21/05 10:17 AM Page 1
Part A. ORDINARY DIFFERENTIAL
EQUATIONS (ODEs)
CHAPTER 1 First-Order ODEs
Major Changes
There is more material on modeling in the text as well as in the problem set.
Some additions on population dynamics appear in Sec. 1.5.
Electric circuits are shifted to Chap. 2, where second-order ODEs will be available.
This avoids repetitions that are unnecessary and practically irrelevant.
Team Projects, CAS Projects, and CAS Experiments are included in most problem sets.
SECTION 1.1. Basic Concepts. Modeling, page 2
Purpose. To give the students a first impression what an ODE is and what we mean by
solving it.
Background Material. For the whole chapter we need integration formulas and
techniques, which the student should review.
General Comments
This section should be covered relatively rapidly to get quickly to the actual solution
methods in the next sections.
Equations (1)–(3) are just examples, not for solution, but the student will see that
solutions of (1) and (2) can be found by calculus, and a solution y = ex of (3) by inspection.
Problem Set 1.1 will help the student with the tasks of
Solving y' = ƒ(x) by calculus
Finding particular solutions from given general solutions
Setting up an ODE for a given function as solution
Gaining a first experience in modeling, by doing one or two problems
Gaining a first impression of the importance of ODEs
without wasting time on matters that can be done much faster, once systematic methods
are available.
Comment on “General Solution” and “Singular Solution”
Usage of the term “general solution” is not uniform in the literature. Some books use the
term to mean a solution that includes all solutions, that is, both the particular and the
singular ones. We do not adopt this definition for two reasons. First, it is frequently quite
difficult to prove that a formula includes all solutions; hence, this definition of a general
solution is rather useless in practice. Second, linear differential equations (satisfying rather
general conditions on the coefficients) have no singular solutions (as mentioned in the
text), so that for these equations a general solution as defined does include all solutions.
For the latter reason, some books use the term “general solution” for linear equations only;
but this seems very unfortunate.
1
, im01.qxd 9/21/05 10:17 AM Page 2
2 Instructor’s Manual
SOLUTIONS TO PROBLEM SET 1.1, page 8
2. y = —e—3x/3 + c 4. y = (sinh 4x)/4 + c
6. Second order. 8. First order.
10. y = ce0.5x, y(2) = ce = 2, c = 2/e, y = (2/e)e0.5x = 0.736e0.5x
12. y = cex + x + 1, y(0) = c + 1 = 3, c = 2, y = 2ex + x + 1
14. y = c sec x, y(0) = c/cos 0 = c = _1π, y = _1π sec x
2 2
16. Substitution of y = cx — c2 into the ODE gives
y'2 — xy' + y = c2 — xc + (cx — c2) = 0.
Similarly,
y = _1x2, y' = _1x, thus _1x2 — x(_1x) + _1x2 = 0.
4 2 4 2 4
18. In Prob. 17 the constants of integration were set to zero. Here, by two integrations,
y” = g, v = y' = gt + c , 1 y = _1gt2 + c t + c ,
2 1 2 y(0) = c = y ,
2 0
and, furthermore,
v(0) = c1 = v0, hence y = _21gt2 + v0 t + y0,
as claimed. Times of fall are 4.5 and 6.4 sec, from t = √1¯ 00/4.9̄ and √2¯
00/4.9̄.
20. y' = ky. Solution y = y0 ekx, where y0 is the pressure at sea level x = 0. Now
y(18000) = y0 ek·18000 = _12y0 (given). From this,
ek·18000 = _1, y(36000) = y ek·2·18000 = y (ek·18000)2 = y (_1)2 = _1y .
2 0 0 0 2 4 0
22. For 1 year and annual, daily, and continuous compounding we obtain the values
ya(1) = 1060.00, yd(1) = 1000(1 + 0.06/365)365 = 1061.83,
yc(1) = 1000e0.06 = 1061.84,
respectively. Similarly for 5 years,
ya(5) = 1000 · 1.065 = 1338.23, yd(5) = 1000(1 + 0.06/365)365·5 = 1349.83,
yc(5) = 1000e0.06·5 = 1349.86.
We see that the difference between daily compounding and continuous compounding
is very small.
The ODE for continuous compounding is yc' = ryc.
SECTION 1.2. Geometric Meaning of y' = ƒ(x, y). Direction Fields, page 9
Purpose. To give the student a feel for the nature of ODEs and the general behavior of
fields of solutions. This amounts to a conceptual clarification before entering into formal
manipulations of solution methods, the latter being restricted to relatively small—albeit
important—classes of ODEs. This approach is becoming increasingly important, especially
because of the graphical power of computer software. It is the analog of conceptual
studies of the derivative and integral in calculus as opposed to formal techniques of
differentiation and integration.
Comment on Isoclines
These could be omitted because students sometimes confuse them with solutions. In the
computer approach to direction fields they no longer play a role.
