System.Math: PI and E meet my requirements of being true global constants. Those values are never going to change, the context for them in almost any application we would build would be universal.

As far as the other methods in Math (and even PI and E to some degree), they are not discoverable by being in System.Math. They are OK as static methods, because they are truly functions, which do not touch other components of the system. They just do their thing and don’t have dependencies. They are also part of the base framework, which makes them less of a problem to be static.

But, I would still rather see a syntax like “32.Math.Cos(3)” which would be extension methods+ a grouping to make it so that I can discover the Math functions available that operate on an integer. This creates a cohesion to the data the static methods operate on, which makes them less “global”.

For System.IO.Path, File and Directory: I would prefer to see those as concrete classes. There really is not a need for them to be static. For example, lets say these classes were to be concrete and implement and interface. Then in your code, you could mock out the interface calls and not have to try to unit test classes that would have to write to the file system.