With the added benefit of having to press not just one, but two buttons in order to add a "+" sign. First press "123", then press "#+=" and now you can add your complex mathematical characters :)
If I have to use the default keyboard to enter arithmetic expressions, I'd rather SSH to my own server. I'm not exactly sure of the privacy implications of typing things into Siri.
With the added benefit of having to press not just one, but two buttons in order to add a "+" sign. First press "123", then press "#+=" and now you can add your complex mathematical characters :)