I am trying to write questions in which students enter the domain of a function in interval notation. I have figured out a way for them to use the infinity symbol, by using a maple graded response with maple syntax and symbolic entry only. When I type "infinity" in the answer, the students can then answer the question using the infinity symbol in the equation editor. There is also a union symbol in the equation editor that I would like them to be able to use, but I have not been able to program it to accept the union symbol as a correct response.