求翻译两个英文句子
in mathematics, it is known that 2 + 2 = 4, but there is also knowing how to add two numbers and knowing a person (e.g., oneself), place (e.g., one's hometown), thing (e.g., cars), or activity (e.g., addition).

A Gettier problem is any one of a category of thought experiments in contemporary epistemology这一句one前面怎么加了个any?