# Trigonometry

Trigonometry (from Greek trigōnon "triangle" + metron "measure") is a branch of mathematics that studies triangles and the relationships between their sides and the angles between these sides. Trigonometry defines the trigonometric functions, which describe those relationships and have applicability to cyclical phenomena, such as waves. The field evolved during the third century BC as a branch of geometry used extensively for astronomical studies. It is also the foundation of the practical art of surveying.

Trigonometry basics are often taught in school either as a separate course or as part of a precalculus course. The trigonometric functions are pervasive in parts of pure mathematics and applied mathematics such as Fourier analysis and the wave equation, which are in turn essential to many branches of science and technology. Spherical trigonometry studies triangles on spheres, surfaces of constant positive curvature, in elliptic geometry. It is fundamental to astronomy and navigation. Trigonometry on surfaces of negative curvature is part of Hyperbolic geometry.

### Other articles related to "trigonometry":

List Of Triangle Topics - Geometry - Trigonometry
... of cosines Law of sines Law of tangents Mollweide's formula Rational trigonometry Solution of triangles Spherical trigonometry Trigonometric functions Trigonometry ...
Spread Polynomials - Use in Rational Trigonometry
... Rational trigonometry is a recently introduced approach to trigonometry that eschews all transcendental functions (such as sine, cosine, etc.), all measurements of angles or compositions of ... The name "spread polynomials" comes from the use of these polynomials in rational trigonometry ...
Applications of Trigonometry
... There are an enormous number of uses of trigonometry and trigonometric functions ... Fields that use trigonometry or trigonometric functions include astronomy (especially for locating apparent positions of celestial objects, in which spherical ...