This site describes solve-engine as it is on main: 2.43.0, which npm does not have yet. npm installs 2.40.0, so a page may show an answer that version does not give yet.
FUNCTION_PACKAGE
const FUNCTION_PACKAGE: IEnginePackage;Defined in: packages/engine/src/packages/function/FunctionPackage.ts:7
Built-in function call syntax, e.g. sqrt(2), sin(pi), dispatches recognized function names to CALL_BUILTIN opcodes.