Obtain real roots

Asked Dec 21 '20 at 19:47

Active Dec 21 '20 at 19:47

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I'm evaluating polynomials that are solvables by radicals in their algebraic solutions but it allways return complex values. Apparently the main issue is with the radicals e.g.

N[(-1)^(1/3)]

returns 0.5 + 0.866025i

instead of -1 (which is the real one of the three roots)

To solve by radicals I need that whenever I ask for a root it assume the real one (possitive if possible),

as in Sqrt[4]

it returns 2 and not -2

asked Dec 21 '20 at 19:47

Ernesto Iglesias

You could e.g. use Solveand specify Reals as domain: Solve[x^3 == -1, x, Reals] – Daniel Huber Dec 21 '20 at 20:25
3

Instead of (-1)^(1/3) use Surd[-1, 3] to get the real root. – Bob Hanlon Dec 21 '20 at 20:26
6

This question has been asked Finding real roots of negative numbers (for example, $\sqrt[3]{-8}$) – Artes Dec 21 '20 at 22:20

Obtain real roots

0 Answers0