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However, for any degree there are some polynomial equations that have algebraic solutions; for example, the equation = can be solved as =. The eight other solutions are nonreal complex numbers , which are also algebraic and have the form x = ± r 2 10 , {\displaystyle x=\pm r{\sqrt[{10}]{2}},} where r is a fifth root of unity , which can be ...
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. For example, 3 is a square root of 9, since 3 2 = 9, and −3 is also a square root of 9, since (−3) 2 = 9.
If only one root, say r 1, is real, then r 2 and r 3 are complex conjugates, which implies that r 2 – r 3 is a purely imaginary number, and thus that (r 2 – r 3) 2 is real and negative. On the other hand, r 1 – r 2 and r 1 – r 3 are complex conjugates, and their product is real and positive. [ 23 ]
Rational numbers have irrationality exponent 1, while (as a consequence of Dirichlet's approximation theorem) every irrational number has irrationality exponent at least 2. On the other hand, an application of Borel-Cantelli lemma shows that almost all numbers, including all algebraic irrational numbers , have an irrationality exponent exactly ...
1800 to 1600 BCE [5] Square root of 3, Theodorus' constant [6] 1.73205 08075 68877 29352 [Mw 3] [OEIS 4] Positive root of = 465 to 398 BCE Square root of 5 [7] 2.23606 79774 99789 69640 [OEIS 5] Positive root of = Phi, Golden ratio [8]
If its minimal polynomial has degree n, then the algebraic number is said to be of degree n. For example, all rational numbers have degree 1, and an algebraic number of degree 2 is a quadratic irrational. The algebraic numbers are dense in the reals. This follows from the fact they contain the rational numbers, which are dense in the reals ...
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 ]
The approximation 161 / 72 (≈ 2.23611) for the square root of five can be used. Despite having a denominator of only 72, it differs from the correct value by less than 1 / 10,000 (approx. 4.3 × 10 −5). As of January 2022, the numerical value in decimal of the square root of 5 has been computed to at least 2,250,000,000,000 ...