Introduction to Trigonometry - Math is Fun
The main functions in trigonometry are Sine, Cosine and Tangent. They are simply one side of a right-angled triangle divided by another. For any angle "θ": (Sine, Cosine and Tangent are often abbreviated to sin, cos and tan.)

Trigonometry | Definition, Formulas, Ratios, & Identities | Britannica
Trigonometry, the branch of mathematics concerned with specific functions of angles. There are six functions commonly used in trigonometry: sine (sin), cosine (cos), tangent (tan), cotangent (cot), secant (sec), and cosecant (csc). Learn more about trigonometry in this article.

Trigonometry - Wikipedia
Trigonometry (from Ancient Greek τρίγωνον (trígōnon) 'triangle' and μέτρον (métron) 'measure') [1] is a branch of mathematics concerned with relationships between angles and side lengths of triangles.

Trigonometry (Functions, Table, Formulas & Examples) - BYJU'S
Trigonometry is a branch that delas with the study of the relationship between sides and angles of a right triangle. Visit BYJU’S to learn the trigonometry formulas, ratios, tables, functions and examples.

Khan Academy
Learn trigonometry concepts such as right triangles, the unit circle, graphs, and identities with Khan Academy.

Sine, Cosine and Tangent - Math is Fun
Sine, Cosine and Tangent are the main functions used in Trigonometry and are based on a Right-Angled Triangle. Before getting stuck into the functions, it helps to give a name to each side of a right triangle: "Opposite" is opposite to the angle θ. "Adjacent" is adjacent to (next to) the angle θ. "Hypotenuse" is the long one.

Trigonometry Definition & Meaning - Merriam-Webster
The meaning of TRIGONOMETRY is the study of the properties of triangles and trigonometric functions and of their applications.

Trigonometry - What is Trigonometry? Formulas, Table, Examples - Cuemath
Trigonometry is the branch of mathematics that deals with the relationship between ratios of the sides of a right-angled triangle with its angles. The ratios used to study this relationship are called trigonometric ratios, namely, sine, cosine, tangent, cotangent, secant, cosecant.

Trigonometric Identities - Math is Fun
The three main functions in trigonometry are Sine, Cosine and Tangent. They are just the length of one side divided by another. For a right triangle with an angle θ : Sine Function: sin (θ) = Opposite / Hypotenuse. Cosine Function: cos (θ) = Adjacent / Hypotenuse. Tangent Function: tan (θ) = Opposite / Adjacent.

Trigonometric functions - Math.net
Trigonometric functions are functions related to an angle. There are six trigonometric functions: sine, cosine, tangent and their reciprocals cosecant, secant, and cotangent, respectively. Sine, cosine, and tangent are the most widely used trigonometric functions. Their reciprocals, though used, are less common in modern mathematics.