Existing bindings

Bindings are mostly rooted from BlueprintFunctionLibrary. Those functions are accessible as context-aware functions within blueprint editor. It is possible to right-click on a node and select "Goto Code Definition" to see the corresponding name in c++. In addition, the file aliases.js declares some handy aliases.

Extending bindings

To extend bindings, I recommend creating a new BlueprintFunctionLibrary class (wiki article). For most of cases it just works.

There are plenty of math functions exposed into BP world by UKismetMathLibraryFunction. There are some edge cases where you cannot access some functions because they are overloaded functions (which have same name but different type of arguments).