Convert symbolic expressions like sqrt(2) or exp(1) to rational numbers [closed]

jjack
17 ●2 ●2 ●6

I have coefficents of a rational polynomial f(x) in terms of symbolic expressions like sqrt(2) and exp(1).

How can I convert these coefficients to rational number approximations of them, so that I can work in a structure like a polynomial ring?

Closed for the following reason the question is answered, right answer was accepted by jjack
close date 2014-07-26 19:57:17.227063

answered 10 years ago

FrédéricC

5436 ●4 ●44 ●121

updated 10 years ago

Maybe something like that:

sage: R.<x> = SR['X']
sage: ex = sqrt(2) + exp(1)*x
sage: realring = RR['x']
sage: ratring = QQ['x']
sage: ratring(realring(ex))
268876667/98914198*x + 131836323/93222358

link

Comments

That sounds good. Is there an advantage in the additional step to working over a field of real numbers? What if I wanted to invert a power series with those coefficients, are rational coeffients better than real numbers?

jjack ( 10 years ago )

Well, you can use either reals or rationals, they will play exactly the same role in any computation with polynomials. If you want rationals, you first need to convert to reals, so that one can then approximate them to rationals. By the way, could you please upvote and accept my answer if it suits you ?

FrédéricC ( 10 years ago )

I'll maybe post a separate question for the precision issue. Thank you for your answer.

jjack ( 10 years ago )

add a comment

Convert symbolic expressions like sqrt(2) or exp(1) to rational numbers [closed]

Closed for the following reason the question is answered, right answer was accepted by jjack
close date 2014-07-26 19:57:17.227063

1 Answer

Comments

Question Tools

Stats

Related questions

Convert symbolic expressions like sqrt(2) or exp(1) to rational numbers [closed] savecancel

Closed for the following reason the question is answered, right answer was accepted by jjack close date 2014-07-26 19:57:17.227063

1 Answer

Comments

Question Tools

Stats

Related questions

Convert symbolic expressions like sqrt(2) or exp(1) to rational numbers [closed]

Closed for the following reason the question is answered, right answer was accepted by jjack
close date 2014-07-26 19:57:17.227063