Final answer:
Stable angina is predictable and controlled with medication, while unstable angina is dangerous and requires urgent medical attention.
Step-by-step explanation:
Stable angina is a diagnosed condition of myocardial ischemia that is predictable in patients. It is characterized by pain in the chest that is precipitated by exertion and improves quickly with rest or medication such as nitroglycerin. On the other hand, unstable angina is a more dangerous type of angina. It is identified by pain that occurs during rest, lasts more than 15 minutes, and is of new onset. This type of angina requires urgent medical attention as it may be a sign of an imminent heart attack.