Theorems in harmonic analysis

Harmonic analysis is a branch of mathematics that studies functions and their representations as sums of basic waves, typically using concepts from Fourier analysis. A number of key theorems have been developed in this field, which can be broadly categorized into various areas. Here are some important theorems associated with harmonic analysis: 1. **Fourier Series Theorem**: This theorem states that any periodic function can be expressed as a sum of sine and cosine functions (or complex exponentials).