After teaching a group of students about angina, the instructor determines that the teaching was successful when the students describe stable angina as:

- Chest pain that is relieved by rest.

Explanation:

Any kind of teaching is considered successful when the instructor/teacher is able to transfer the information about the concept successfully to their students and they are able to answer the questions or solve the problems associated to the concept appropriately.

In the given situation, the teaching would be determined successful as the teacher was able to describe stable angina appropriately as 'Chest pain that is relieved by rest' that reflects the teacher has successfully delivered the concept to their minds. The students' answer(problem-solving') is reflective of that as it enhanced their knowledge and performance both.