[Math] How to construct a transcendental number

transcendental-numbers

I am doing a project about irrational and transcendental numbers and I was wondering how could I construct a "new" transcendental number. I know that all Liouville numbers are transcendental so this could be a good place to start however I wish to try and create one not necessarily belonging to that group of numbers. In addition to this I am aware of Liouville's theorem surrounding transcendental numbers and have also found a proof to how that the theorem is true and holds for Liouville's constant.

Once again I know about the Gelfond-Schneider theorem but the same idea applies. I would like to stay away from obvious substitutions i.e. $4^{\sqrt{17}}$ is transcendental but not really "interesting". Also any strange theorems I would like to try and prove for the sake of completion. I don't want to just assert something and just have it there. I would like to be as thorough as possible.

Any help is greatly appreciated and thanks in advance

Best Answer

Take your favorite polynomial, $p(x) := x^2-x-1$, and your favorite transcendental number $c := \pi$. The number $p(c)$ is transcendental.

The key to transcendental numbers is polynomials with integer or rational coefficients. If $p(c)$ was algebraic, then there exists polynomials $q(x)$ such that $q(p(c))=0$ but then the composition $r(x):=q(p(x))$ is also a polynomial and $r(c)=0$ which would imply that $c$ is algebraic. The contrapositive statement is now proven.

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