Homework 4, due October 1, 2014

[goodwine]

Reading: Chapters 3 and 4.

Exercises: 3.2, 3.10, 3.12, 3.18 (parts 1, 2, and 7 only), 3.21, 3.28 and 3.29.

As a reminder, the syllabus states you may not consult homework solutions from prior years, solution manuals, etc. If you don't know how to even start a problem, using solutions as a guide is still disallowed because perhaps the entire point of the problem is how to start. Regardless, come to my office hours, or post a question on here. The point isn't to complete the homework for credit, it's to learn something.

[jackgoza]

Did anyone else have their cos and sin coefficients cancel during method of undetermined coefficients and if so, can you assume they're covered by the homogeneous solution? Please advise.

[goodwine]

Did anyone else have their cos and sin coefficients cancel during method of undetermined coefficients and if so, can you assume they're covered by the homogeneous solution? Please advise.

Which problem?

[jackgoza]

3.18 number 7.

[goodwine]

3.18 number 7.

What did you get for the homogeneous solutions?

[jackgoza]

X_h= k_1 cos(4t) + k_2 sin(4t).

For my coefficients I got:
Cos: 4C_1 - 4C_1 = 1
Sin: 4C_2 - 4C_2 = 1

[goodwine]

X_h= k_1 cos(4t) + k_2 sin(4t).

For my coefficients I got:
Cos: 4C_1 - 4C_1 = 1
Sin: 4C_2 - 4C_2 = 1

I'm pretty sure those are incorrect. Your difficulties in computing x_p give a good clue as to what they should be.

[jackgoza]

Awesome I'll double check those. Thanks!