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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 first tables of trigonometric functions known to be made were by Hipparchus (c.190 – c.120 BCE) and Menelaus (c.70–140 CE), but both have been lost. Along with the surviving table of Ptolemy (c. 90 – c.168 CE), they were all tables of chords and not of half-chords, that is, the sine function. [1]
Trigonometric functions were among the earliest uses for mathematical tables. [48] Such tables were incorporated into mathematics textbooks and students were taught to look up values and how to interpolate between the values listed to get higher accuracy. [49] Slide rules had special scales for trigonometric functions. [50]
In mathematics, the values of the trigonometric functions can be expressed approximately, as in (/), or exactly, as in (/) = /.While trigonometric tables contain many approximate values, the exact values for certain angles can be expressed by a combination of arithmetic operations and square roots.
This identity and analogous relationships between the other trigonometric functions are summarized in the following table. Top: Trigonometric function sin θ for selected angles θ, π − θ, π + θ, and 2 π − θ in the four quadrants. Bottom: Graph of sine versus angle. Angles from the top panel are identified.
The following table gives an overview of Green's functions of frequently appearing differential operators, where = + +, = +, is the Heaviside step function, () is a Bessel function, () is a modified Bessel function of the first kind, and () is a modified Bessel function of the second kind. [2]
The following functions and variables are used in the table below: δ represents the Dirac delta function. u(t) represents the Heaviside step function. Literature may refer to this by other notation, including () or (). Γ(z) represents the Gamma function. γ is the Euler–Mascheroni constant. t is a real number.
The versine or versed sine is a trigonometric function found in some of the earliest (Sanskrit Aryabhatia, [1] Section I) trigonometric tables.The versine of an angle is 1 minus its cosine.