They used the Remez exchange algorithm to find the polynomial with minimax relative error. https://en.wikipedia.org/wiki/Remez_algorithm https://en.wikipedia.or

They used the Remez exchange algorithm to find the polynomial with minimax relative error. https://en.wikipedia.org/wiki/Remez_algorithm https://en.wikipedia.org/wiki/Remez_algorithm If you want to play with this sort of thing and you have access to a copy of Matlab, check out Chebfun, https://www.chebfun.org/examples/approx/ https://www.chebfun.org/examples/approx/