Final answer:
The golfer is likely experiencing stable angina, which is chest pain relieved by rest and sublingual nitroglycerin, and typically triggered by physical exertion.
Step-by-step explanation:
The type of angina the 74-year-old professional golfer is experiencing is stable angina. This condition is characterized by chest pain that occurs with exertion, such as playing golf, and is quickly relieved by rest and by taking sublingual nitroglycerin, which helps by dilating the coronary arteries and improving blood flow. Stable angina is distinguished from unstable angina, which is more serious, occurs at rest, can last for longer than 15 minutes, and may indicate an approaching heart attack, requiring immediate medical attention.