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The positive integer n is called the index or degree, and the number x of which the root is taken is the radicand. A root of degree 2 is called a square root and a root of degree 3, a cube root. Roots of higher degree are referred by using ordinal numbers, as in fourth root, twentieth root, etc. The computation of an n th root is a root extraction.
Since the root of unity is a root of the polynomial x n − 1, it is algebraic. Since the trigonometric number is the average of the root of unity and its complex conjugate, and algebraic numbers are closed under arithmetic operations, every trigonometric number is algebraic. [2]
When p = ±3, the above values of t 0 are sometimes called the Chebyshev cube root. [29] More precisely, the values involving cosines and hyperbolic cosines define, when p = −3, the same analytic function denoted C 1/3 (q), which is the proper Chebyshev cube root. The value involving hyperbolic sines is similarly denoted S 1/3 (q), when p = 3.
The mean value theorem ensures that if there is a root of f in X k, then it is also in X k + 1. Moreover, the hypothesis on F′ ensures that X k + 1 is at most half the size of X k when m is the midpoint of Y , so this sequence converges towards [ x* , x* ] , where x* is the root of f in X .
A formula for computing the trigonometric identities for the one-third angle exists, but it requires finding the zeroes of the cubic equation 4x 3 − 3x + d = 0, where is the value of the cosine function at the one-third angle and d is the known value of the cosine function at the full angle.
[1] [2] One reason for this is that they can greatly simplify differential equations that do not need to be answered with absolute precision. There are a number of ways to demonstrate the validity of the small-angle approximations. The most direct method is to truncate the Maclaurin series for each of the trigonometric functions.
Complex numbers thus form an algebraically closed field, where any polynomial equation has a root. Many mathematicians contributed to the development of complex numbers. The rules for addition, subtraction, multiplication, and root extraction of complex numbers were developed by the Italian mathematician Rafael Bombelli. [24]
The square root of 2 is equal to the length of the hypotenuse of a right triangle with legs of length 1 and is therefore a constructible number. In geometry and algebra, a real number is constructible if and only if, given a line segment of unit length, a line segment of length | | can be constructed with compass and straightedge in a finite number of steps.