Friday, July 22, 2005

Differential Equations Aftermath

No notes, no book, no calculators allowed. 60 minutes.
I finished all but one of the problems in 15 minutes.
I had the test completely finished after 25 minutes.

I spent the rest of the time checking over my answers, and of course, I didn't check carefully enough.

There were 6 problems. I got 5 of them. I missed the third problem by mistakenly claiming that sqrt(-4) = sqrt(2)i, which obviously should have been 2i. That was an incredibly careless mistake. Even though it was just a mistake in calculation it also made the rest of my solution very wrong.

(The rest of the problem, besides finding the solution, was to use Euler's formula to get the real-domain answer from the complex general answer, which was not that difficult.)

I also missed the sixth problem.
The problem was something similar to the following:

Give the general solution for y.

y'' + (2y' * ln(y'))^2 + y ln(y) = 0

At first I looked at it and panicked because we never had to do a second-order ODE problem where we couldn't just use the characteristic equation to easily solve it.

...

I have to do the take-home portion now.

My next test is an electrical engineering test on Wednesday. yahoo...