Sine, Cosine, Tangent and the Unit Circle - Wolfram Demonstrations

List of trigonometric identities - Wikipedia

A Sine/Cosine Identity - Wolfram Demonstrations Project

sin cos tan – Geeks out of the box

Illustrating Cotangent with the Unit Circle - Wolfram Demonstrations Project

How do tan, sin and cos work? - Quora

Unit circle - Wikipedia

Illustrating Secant with the Unit Circle - Wolfram Demonstrations Project

Launching Version 12.2 of Wolfram Language & Mathematica: 228 New Functions and Much More…—Stephen Wolfram Writings

Versine - Wikipedia

Graphing Trigonometric Functions

Angles Measured in Degrees and Radians - Wolfram Demonstrations Project

Example: Graphing the Tangent Function Using the Unit Circle and the Reciprocal Identity

Archaic Trigonometry - Wolfram Demonstrations Project

Visualizing Parametrized Curves