Bill Goodwine's Courses

Reading: For the upcoming exam, you are responsible for all the material in Chapters 1 through 4, with the exception of section 1.6.

Exercises: 4.3, 4.4, 4.7, 4.9, 4.10, 4.12, 4.14, 4.19 and 4.22.

For 4.4, we need to determine the approximations to the steady solutions for the equations. What do you mean by good approximations? I can find out the values for magnification factor and phase shift from the plots made in 4.3. Should I also plot the particular solutions to the equations?

ypan1 wrote:For 4.4, we need to determine the approximations to the steady solutions for the equations. What do you mean by good approximations? I can find out the values for magnification factor and phase shift from the plots made in 4.3. Should I also plot the particular solutions to the equations?

The point of the problem is to use those plots to find the approximate particular (steady-state) solution. So, the particular solution and the solutions from the plots should be the same.

Can we just eye up the graphs for problem 4.4 to get an approximation or should we use the equations for the magnification factor and the phase shift?

sprender wrote:Can we just eye up the graphs for problem 4.4 to get an approximation or should we use the equations for the magnification factor and the phase shift?

The former -- the point of the problem is to use the graphs.

I'm having trouble graphing my inverse tan function in matlab for question 4.3 part 4

Heres the code I have:

r = linspace(0,5,1000);
z = 0.2;
x = atan((1.-r.^2)/(2.*z.*r));
plot (r,x)

any suggestions?...

...sorry, the problem i'm having is that its only returning a straight horizontal line for the graph...i also tried just doing the one already in the book on page 98 and the same thing was happening for that one as well.

mhubbar3 wrote:...sorry, the problem i'm having is that its only returning a straight horizontal line for the graph...i also tried just doing the one already in the book on page 98 and the same thing was happening for that one as well.

I can't see anything wrong, at least initially. If you type 'x' to see what x is, what does it give? A bunch of different numbers, or a constant one? The only possible issue I can see right now is that / maybe should be ./ Also, you don't need .* for the 2 and zeta terms since those are constants.

goodwine wrote:

mhubbar3 wrote:...sorry, the problem i'm having is that its only returning a straight horizontal line for the graph...i also tried just doing the one already in the book on page 98 and the same thing was happening for that one as well.

I can't see anything wrong, at least initially. If you type 'x' to see what x is, what does it give? A bunch of different numbers, or a constant one? The only possible issue I can see right now is that / maybe should be ./ Also, you don't need .* for the 2 and zeta terms since those are constants.

Now that I think about it, I'm > 90% sure it's the ./ If that fixes it, it's probably worthwhile to figure out why.

that worked, thanks