In trigonometry, trigonometric identities are equalities that involve trigonometric functions and are true for every value of the occurring variables for which both sides of the equality are defined. Geometrically, these are identities involving certain functions of one or more angles.They are distinct from triangle identities, which are identities potentially involving angles but also ...

Radians Degrees sin cos tan cot sec csc + + + + + + + + + + + + + + + + + + + + + + + + Expressibility with square roots. Some exact trigonometric values, such as ⁡ = /, can be expressed in terms of a combination of arithmetic operations and square roots.Such numbers are called constructible, because one length can be constructed by compass and straightedge …

In mathematics, tables of trigonometric functions are useful in a number of areas. Before the existence of pocket calculators, trigonometric tables were essential for navigation, science and engineering.The calculation of mathematical tables was an important area of study, which led to the development of the first mechanical computing devices.

The differentiation of trigonometric functions is the mathematical process of finding the derivative of a trigonometric function, or its rate of change with respect to a variable.For example, the derivative of the sine function is written sin′(a) = cos(a), meaning that the rate of change of sin(x) at a particular angle x = a is given by the cosine of that angle.

Early study of triangles can be traced to the 2nd millennium BC, in Egyptian mathematics (Rhind Mathematical Papyrus) and Babylonian mathematics.Trigonometry was also prevalent in Kushite mathematics. Systematic study of trigonometric functions began in Hellenistic mathematics, reaching India as part of Hellenistic astronomy. In Indian astronomy, the study of …

Several notations for the inverse trigonometric functions exist. The most common convention is to name inverse trigonometric functions using an arc- prefix: arcsin(x), arccos(x), arctan(x), etc. (This convention is used throughout this article.) This notation arises from the following geometric relationships: [citation needed] when measuring in radians, an angle of θ radians will …

There are several equivalent ways for defining trigonometric functions, and the proof of the trigonometric identities between them depend on the chosen definition. The oldest and somehow the most elementary definition is based on the geometry of right triangles.The proofs given in this article use this definition, and thus apply to non-negative angles not greater than a right angle.

The trigonometric Fourier series enables one to express a periodic function (or a function defined on a closed interval [a,b]) as an infinite sum of trigonometric functions (sines and cosines). In this sense, the Fourier series is analogous to Taylor series, since the latter allows one to express a function as an infinite sum of powers.

Trigonometric ratios can also be represented using the unit circle, which is the circle of radius 1 centered at the origin in the plane. In this setting, the terminal side of an angle A placed in standard position will intersect the unit circle in a point (x,y), where = ⁡ and = ⁡. This representation allows for the calculation of commonly found trigonometric values, such as those in the ...

The Pythagorean trigonometric identity, also called simply the Pythagorean identity, is an identity expressing the Pythagorean theorem in terms of trigonometric functions.Along with the sum-of-angles formulae, it is one of the basic relations between the sine and cosine functions.. The identity is ⁡ + ⁡ = As usual, sin 2 θ means (⁡)