220_pdfsam_math 54 differential equation solutions odd

# 220_pdfsam_math 54 differential equation solutions odd - v...

This preview shows page 1. Sign up to view the full content.

Chapter 4 7. The auxiliary equation in this problem is r 2 +16 = 0, which has the roots r = ± 4 i . Therefore, y 1 ( θ )=cos4 θ and y 2 ( θ )=s in4 θ are two linearly independent solutions, and a general solution to the corresponding homogeneous equation is given by y h ( θ )= c 1 cos 4 θ + c 2 sin 4 θ. Using the variation of parameters method, we look for a particular solution to the original nonhomogeneous equation of the form y p ( θ )= v 1 ( θ ) y 1 ( θ )+ v 2 ( θ ) y 2 ( θ )= v 1 ( θ )cos4 θ + v 2 ( θ )sin4 θ. The system (9) on page 195 in the text becomes v 0 1 ( θ )cos4 θ + v 0 2 ( θ )sin4 θ =0 , 4 v 0 1 ( θ )sin4 θ +4 v 0 2 ( θ )cos4 θ =sec4 θ. (4.7) Multiplying the Frst equation in (4.7) by sin 4 θ and the second equation by (1 / 4) cos 4 θ ,and adding the resulting equations together, we get v 0 2 ( θ )= 1 4 v 2 = 1 4 θ + c 3 .
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: v 1 ( ) = 1 4 tan 4 v 1 ( ) = 1 4 Z tan 4 d = 1 16 ln | cos 4 | + c 4 . Taking c 3 = c 4 = 0, we obtain y p ( ) = cos 4 16 ln | cos 4 | + 1 4 sin 4 y ( ) = c 1 cos 4 + c 2 sin 4 + 4 sin 4 + cos 4 16 ln | cos 4 | . 9. In this problem, the corresponding homogeneous equation is the same as that in Problem 1. Hence y 1 ( t ) = cos 2 t and y 2 ( t ) = sin 2 t are two linearly independent solutions, and a general solution to the homogeneous equation is given by y h ( t ) = c 1 cos 2 t + c 2 sin 2 t, 216...
View Full Document

## This note was uploaded on 03/29/2010 for the course MATH 54257 taught by Professor Hald,oh during the Spring '10 term at University of California, Berkeley.

Ask a homework question - tutors are online