## Homework 7, due October 27, 2011.

Due at noon Thursday, October 27, 2011.
goodwine
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### Homework 7, due October 27, 2011.

Reading: All of Chapter 5. More details than usual were left for the reading for this assignment, so it is more important than usual to do the reading this week.

Exercises: 5.7-5.10, 5.16 and 5.19.
Bill Goodwine, 376 Fitzpatrick
Hopz

### Re: Homework 7, due October 27, 2011.

The Airy Eqn is written differently in question 5.7 than what ch.5.5.1 provides. So I am guessing that we should solve for the eqn given in the problem?

5.9 gives:
d2y /dx2 (x)+xy(x) = 0.

While Ch, 5.51 gives:
d2y/dx2 (x)−xy(x) = 0
jconcelm

### Re: Homework 7, due October 27, 2011.

For question 5.16, the equation uses dy/dt but then is multiplied by x. I am confused as to what to do with 3 variables because we are assuming a solution that only involves y and x. In example 5.7 in the book you substitute dy/dx for dy/dt. Is this acceptable?
goodwine
Posts: 1596
Joined: Tue Aug 24, 2004 4:54 pm
Location: 376 Fitzpatrick
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### Re: Homework 7, due October 27, 2011.

Hopz wrote:The Airy Eqn is written differently in question 5.7 than what ch.5.5.1 provides. So I am guessing that we should solve for the eqn given in the problem?

5.9 gives:
d2y /dx2 (x)+xy(x) = 0.

While Ch, 5.51 gives:
d2y/dx2 (x)−xy(x) = 0
Do it the way that is stated in the problem. They are just different forms of the Airy Equation.
Bill Goodwine, 376 Fitzpatrick
goodwine
Posts: 1596
Joined: Tue Aug 24, 2004 4:54 pm
Location: 376 Fitzpatrick
Contact:

### Re: Homework 7, due October 27, 2011.

jconcelm wrote:For question 5.16, the equation uses dy/dt but then is multiplied by x. I am confused as to what to do with 3 variables because we are assuming a solution that only involves y and x. In example 5.7 in the book you substitute dy/dx for dy/dt. Is this acceptable?
That's a big typo. The independent variable is x, so both derivative terms should be with respect to x.
Bill Goodwine, 376 Fitzpatrick
Jessie

### Re: Homework 7, due October 27, 2011.

for problem 5.19 I am confused on how to get the value for a0. Do we need initial conditions?
goodwine