MATHS 361 Tutorial 3
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DEPARTMENT OF MATHEMATICS
MATHS 361
Tutorial 3
The aim of this tutorial is to become more familiar with Sturm-Liouville problems.
1. Which of the following BVPs are regular Sturm Liouville problems? Give rea- sons for your answers.
(a) y// + y + λy = 0, -π < x < π ,
y(-π) = 0, y(π) = 0
(b) y// + 2y/ + λy = 0, 0 < x < 1,
y(0) = 0, y(1) - 4y/ (1) = 0
(c) 2y// + y + λy = 0, 0 < x < o ,
y(0) = 0, limz二o y/ (x) = 0
(d) xy// + y/ + λxy = 0, 0 < x < 1,
y(0) = 0, y(1) = 0
(e) xy// + y/ + y + λxy = 0, 1 < x < 3,
y/ (1) = 0, y(3) = 0
2. By checking the conditions in the relevant theorem presented in class, show that
each of the following Sturm Liouville problems has no negative eigenvalues.
(a) y// + λy = 0 for x ∈ (0, 2), y(0) = 0, y/ (2) = 0.
(b) (1 + x2 )y// + 2xy/ + λy = 0 for x ∈ (0, 2), y/ (0) - y(0) = 0, y(2) = 0.
3. Determine whether zero is an eigenvalue for each of the following SLPs. In each case, if the answer is yes, find the corresponding eigenfunction.
(a) y// + λy = 0, y/ (-1) = 0, y/ (1) = 0.
(b) y// + λy = 0, y(-1) + y/ (-1) = 0, y/ (1) = 0.
4. The SLP y// + λy = 0, y(0) = 0, y/ (π) = 0 has the eigenvalues λn = (n - 1/2)2
for n = 1, 2, . . . with corresponding eigenfunctions φn = sin /n - x.
(a) Write down the weight function for this SLP.
(b) Express the function f (x) = x, x ∈ [0, π] as an infinite sum of the eigen- functions. Compute all the coefficients in the sum.
5. Compute the eigenvalues and eigenfunctions for the following SLP:
y// + 2y + λy = 0, y/ (0) = 0, y(π) = 0.
Hint: Write µ = 2 + λ .
6. Challenge question: Use matlab1 to compute the smallest three positive values of λ such that taneλ = -eλ. Give your answers with three significant figures of accuracy.
2023-06-24