Not sure the acet functions are in Intellicad. Copying them from Autocad may breach copyrite.
2nd question how do you use the acet function there is so little documentation out there spent 1/2 hour already finding nothing. All I found was the list of 300 items and a few details on afra lisp.
Trial and error (acet-geom-intersectwith (car ent2) (car ent1) 3) similar to intersectwith has extend modes. 2 lines is 3, an arc - line can be 3 or 1.
acExtendNone Does not extend either object.
acExtendThisEntity Extends the base object.
acExtendOtherEntity Extends the object passed as an argument.
acExtendBoth Extends both objects.