Extended Trig Methods

[SMcNeill]

@dbox to be a total nag, it seems to me a more productive use of time to get _Maptriangle working than exotic math functions.

The only people that would use exotic math functions can create their own from building blocks of the basic ones such as Sin, Cos and Tan and their Arc- prefixes because they would be quite familiar with and skilled at using Trig Indentities.

What's wrong with _MapTriangle?