As per https://github.com/scala/scala-dev/issues/661 , we can’t add stuff to the standard library at the moment.
Consider using a third-party package such as Spire.
I would add that it’s somewhat unclear what Numeric's ambition level is or should be. I want to say that Numeric doesn’t aim to provide all the math operations one might want. It exists to support operations such as .sum and .product. It doesn’t have bigger ambitions than that. But it’s not really that simple, because there are things in Numeric that don’t really need to be there afaict. I suspect that back when Numeric was introduced, it was unclear what the eventual ambition level might end up being.