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  2. List of trigonometric identities - Wikipedia

    en.wikipedia.org/wiki/List_of_trigonometric...

    Ptolemy's theorem states that the sum of the products of the lengths of opposite sides is equal to the product of the lengths of the diagonals. When those side-lengths are expressed in terms of the sin and cos values shown in the figure above, this yields the angle sum trigonometric identity for sine: sin(α + β) = sin α cos β + cos α sin β.

  3. Inverse trigonometric functions - Wikipedia

    en.wikipedia.org/wiki/Inverse_trigonometric...

    The most common convention is to name inverse trigonometric functions using an arc- prefix: arcsin(x), arccos(x), arctan(x), etc. [1] (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 correspond to an arc ...

  4. atan2 - Wikipedia

    en.wikipedia.org/wiki/Atan2

    atan2(y, x) returns the angle θ between the positive x-axis and the ray from the origin to the point (x, y), confined to (−π, π].Graph of ⁡ (,) over /. In computing and mathematics, the function atan2 is the 2-argument arctangent.

  5. Equation of time - Wikipedia

    en.wikipedia.org/wiki/Equation_of_time

    The correct branch of the multiple valued function arctan x to use is the one that makes ν a continuous function of E(M) starting from ν E=0 = 0. Thus for 0 ≤ E < π use arctan x = arctan x, and for π < E ≤ 2π use arctan x = arctan x + π. At the specific value E = π for which the argument of tan is infinite, use ν = E.

  6. Hyperbolic secant distribution - Wikipedia

    en.wikipedia.org/wiki/Hyperbolic_secant_distribution

    where "arctan" is the inverse (circular) tangent function. Johnson et al. (1995) [1]: 147 places this distribution in the context of a class of generalized forms of the logistic distribution, but use a different parameterisation of the standard distribution compared to that here.

  7. Inverse tangent integral - Wikipedia

    en.wikipedia.org/wiki/Inverse_tangent_integral

    The inverse tangent integral is defined by: ⁡ = ⁡ The arctangent is taken to be the principal branch; that is, − π /2 < arctan(t) < π /2 for all real t. [1]Its power series representation is

  8. Expected value - Wikipedia

    en.wikipedia.org/wiki/Expected_value

    According to this definition, E[X] exists and is finite if and only if E[X +] and E[X −] are both finite. Due to the formula |X| = X + + X −, this is the case if and only if E|X| is finite, and this is equivalent to the absolute convergence conditions in the definitions above. As such, the present considerations do not define finite ...

  9. Trigonometry - Wikipedia

    en.wikipedia.org/wiki/Trigonometry

    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 = ⁡. [37] This representation allows for the calculation of commonly found trigonometric values, such as those in the following table: [ 38 ]