# Algorithm to convert rendered number back into symbolic form

If you have a number such as $3.14626437$ and you need to know what symbols create it, as far as I know, there are two tools:

1- ISC

and the answer is $\sqrt2+\sqrt3$

I am wondering what algorithm these websites are using and how much is their complexity?

If you do a Google search for algorithm for inverse symbolic calculator, you will find Wikipedia's page on algorithms for finding integer relations between multiple real numbers (as the page describes, you look for an integer relation between $x$, the number you care about, and a list of other standard mathematical constants).