# History of trigonometric functions

The sine, tangent, and secant functions of an angle constructed geometrically in terms of a unit circle. There are several fundamental differences between planar and spherical triangles. The tangent of an angle is the ratio of the length of the opposite side to the length of the adjacent side: Many similar constructions are possible, and the basic trigonometric identities can also be proven graphically.

The 17th and 18th centuries saw the invention of numerous mechanical devices—from accurate clocks and navigational tools to musical instruments of superior quality and greater tonal range—all of which required at least some knowledge of trigonometry.

With the Greeks we first find a systematic study of relationships between angles or arcs in a circle and the lengths of chords subtending these. Application to science While these developments shifted trigonometry away from its original connection to triangles, the practical aspects of the subject were not neglected.

The arcsine, for example, can be written as the following integral: For example, two spherical triangles whose angles are equal in pairs are congruent identical in size as well as in shapewhereas they are only similar identical in shape for the planar case.

But pre-Hellenic societies lacked the concept of an angle measure and consequently, the sides of triangles were studied instead, a field that would be better called "trilaterometry". Its author, Aryabhata I c. The secant and cosecant were not used by the early astronomers or surveyors. The second book of the Sphaerica describes the application of spherical geometry to astronomical phenomena and is of little mathematical interest. It was Leonhard Euler who fully incorporated complex numbers into trigonometry.

The hyperbolic trigonometric functions were introduced by Lambert. Rheticus also produced substantial tables of sines and cosines which were published after his death.

However, it appears that not until Hipparchus undertook the task had anyone tabulated corresponding values of arc and chord for a whole series of angles.

Calculus For integrals and derivatives of trigonometric functions, see the relevant sections of Differentiation of trigonometric functions, Lists of integrals and List of integrals of trigonometric functions.

The thirteen books of the Almagest are the most influential and significant trigonometric work of all antiquity. The superposition of several terms in the expansion of a sawtooth wave are shown underneath. He lived in Alexandriathe intellectual centre of the Hellenistic world, but little else is known about him.

Menelaus and his Greek successors instead referred to AB simply as the chord corresponding to the arc AB. Uses of trigonometry The trigonometric functions, as the name suggests, are of crucial importance in trigonometry, mainly because of the following two results. The six trigonometric functions can be defined as coordinate values of points on the Euclidean plane that are related to the unit circlewhich is the circle of radius one centered at the origin O of this coordinate system.

Indian mathematics Statue of Aryabhata. These six trigonometric functions in relation to a right triangle are displayed in the figure. On Triangles contains all the theorems needed to solve triangles, planar or spherical—although these theorems are expressed in verbal form, as symbolic algebra had yet to be invented.

Also, for purely real x, It is also sometimes useful to express the complex sine and cosine functions in terms of the real and imaginary parts of their arguments. Menelaus proved a property of plane triangles and the corresponding spherical triangle property known the regula sex quantitatum.

Egyptian mathematics The Egyptians, on the other hand, used a primitive form of trigonometry for building pyramids in the 2nd millennium BC. That is, for any similar triangle the ratio of the hypotenuse for example and another of the sides remains the same. The Rhind papyrusan Egyptian collection of 84 problems in arithmeticalgebra, and geometry dating from about bce, contains five problems dealing with the seked.

The mnemonic "all science teachers are crazy" lists the functions which are positive from quadrants I to IV. Thales used the lengths of shadows to calculate the heights of pyramids.

For example, problem 56 asks:. The functions (also called the circular functions) comprising trigonometry: the cosecant cscx, cosine cosx, cotangent cotx, secant secx, sine sinx, and tangent tanx. However, other notations are sometimes used, as summarized in the following table.

f(x) alternate notations cotx ctnx (Erdélyi et al.p. 7), ctgx (Gradshteyn and Ryzhikp. xxix) cscx cosecx (Gradshteyn and Ryzhik Trigonometry, the branch of mathematics concerned with specific functions of angles and their application to calculations.

There are six functions of an angle commonly used in trigonometry. Their names and abbreviations are sine (sin), cosine (cos), tangent (tan), cotangent (cot), secant (sec), and cosecant (csc).

These six trigonometric functions in relation to a right triangle are displayed. History of Trigonometry The first trigonometric table was apparently compiled by Hipparchus, who is. Trigonometry (from Greek trigōnon, "triangle" and metron, "measure") is a branch of mathematics that studies relationships involving lengths and angles of thesanfranista.com field emerged in the Hellenistic world during the 3rd century BC from applications of geometry to astronomical studies.

The 3rd-century astronomers first noted that the lengths of the sides of a right-angle triangle and the. Trigonometry, the branch of mathematics concerned with specific functions of angles and their application to calculations. There are six functions of an angle commonly used in trigonometry. There are six functions of an angle commonly used in trigonometry. Learn how to solve trigonometric equations and how to use trigonometric identities to solve various problems.

History of trigonometric functions
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Trigonometric functions - Wikipedia