[AMath 383] Comments on HW #2
Class,
Okay, I'm glad that a few students are dropping by to talk with me. I
want to clarify a few things about the homework.
First, in the warm-ups (I hope you're doing them :-), problem 3 should
have been expressed as ky on the right hand side and not kx.
For required problem 1, part b, some are wondering about the
significance of characteristic scales. I want you to look at your
solution and identify where the characteristic time scale appears in
the solution. Also, where does the characteristic money scale appear?
Beyond this, I want you to try to think about how these scales might
relate to the graph. What happens if you consider the time t when it
actually reaches the characteristic time? What has happened to the
solution? What happens to the solution if the money balance is equal to
the characteristic balance? What if it is bigger? What if it is
smaller? Why would this be significant?
For part (d), be sure that you find the MONTHLY payment for a 30 YEAR
loan. Make sure that this is what your loan calculator is really
computing. (I don't expect you to find the formula for true monthly
payments as computed by these calculators--that's why I suggest you
look online.)
For problem 2, I strongly suggest that you consider expressing the
differential equations in terms of proportionality constants rather
than trying to keep track of all the different appearances of the
constant pi. Do both parts (a) and (b) before moving to part (c).
Sincerely,
D. Brian Walton
AMath 383 Instructor
Guggenheim 408C
(206) 685-9298