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[1] [10] Another precarious convention used by a small number of authors is to use an uppercase first letter, along with a “ −1 ” superscript: Sin −1 (x), Cos −1 (x), Tan −1 (x), etc. [11] Although it is intended to avoid confusion with the reciprocal, which should be represented by sin −1 (x), cos −1 (x), etc., or, better, by ...
Basis of trigonometry: if two right triangles have equal acute angles, they are similar, so their corresponding side lengths are proportional.. In mathematics, the trigonometric functions (also called circular functions, angle functions or goniometric functions) [1] are real functions which relate an angle of a right-angled triangle to ratios of two side lengths.
If the logarithm of exsecant is calculated by looking up the secant in a six-place trigonometric table and then subtracting 1, the difference sec 1° − 1 ≈ 0.000 152 has only 3 significant digits, and after computing the logarithm only three digits are correct, log(sec 1° − 1) ≈ −3.81 8 156. [24]
Sec-1, SEC-1, sec-1, or sec −1 may refer to: sec x−1 = sec(x)−1 = exsec(x) or exsecant of x, an old trigonometric function; sec −1 y = sec −1 (y), sometimes interpreted as arcsec(y) or arcsecant of y, the compositional inverse of the trigonometric function secant (see below for ambiguity)
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.
In contrast, by the Lindemann–Weierstrass theorem, the sine or cosine of any non-zero algebraic number is always transcendental. [4] The real part of any root of unity is a trigonometric number. By Niven's theorem, the only rational trigonometric numbers are 0, 1, −1, 1/2, and −1/2. [5]
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y = arccos(x) x = cos(y) −1 ≤ x ≤ 1: 0 ≤ y ≤ π: 0° ≤ y ≤ 180° arctangent: y = arctan(x) x = tan(y) all real numbers: − π / 2 < y < π / 2 −90° < y < 90° arccotangent: y = arccot(x) x = cot(y) all real numbers 0 < y < π: 0° < y < 180° arcsecant: y = arcsec(x) x = sec(y) x ≤ −1 or 1 ≤ x: 0 ≤ y ...