Section 25.4

Fourier Sine Series

If we odd-extend a function defined on , we can use just sines.

1

Introduction

This series is natural for problems with Dirichlet conditions (like the string).

2

The Coefficients

Formula


3

Worked Examples

Example 1: Square Wave

Expand on .

.

.

If n even, 0. If n odd, .

.

Example 2: Visualizing

Gibbs Phenomenon: The overshoot at jump discontinuities.

Example 3: Interpretation

What does this mean physically?

If a string is plucked in a flat shape (impossible, but theoretical), it creates these harmonics.

The "sound" component has amplitude .

4

Practice Quiz

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