# Polynomial approximation (with decreasing error preferably) of Bessel functions

The functions: $$J_1(a\sqrt x) = ??$$ $$I_1(a\sqrt x) = ??$$ s.t. $$a, \sqrt x \in R$$

See the first answer to a question I've asked previously for an example of what I'd be looking for.

Please provide a function approximating the following hypergeometric series?

• Are you looking for approximations for small or large values of the argument ? Jun 11, 2019 at 4:14
• @ClaudeLeibovici Large values of the argument, and any domain exceptions. Positive numbers preferred, will take answers about negative numbers too. Jun 12, 2019 at 18:42