periodic function

A Fourier series represents a periodic function as an infinite sum of sine and cosine functions.

The tangent function \(f(x) = \tan(x)\) assigns to each angle \(x\), expressed in radians, its corresponding tangent value.

\[ \tan(x) = \frac{\sin(x)}{\cos(x)} \]

The cotangent function \( f(x) = \cot(x) \) assigns to each angle \( x \), expressed in radians, its corresponding cotangent value.

\[
\cot(x) = \frac{\cos(x)}{\sin(x)}
\]