我在高三时选修了微积分，我非常喜欢我们的老师在第一天上课时提出的这个问题。

他要求有人举手问他，我们什么时候会在日常生活中使用微积分。于是一个学生举手问道："我们什么时候能在日常生活中使用这个？"

"永远不会！！"老师感叹道。"你们在正常的日常生活中永远不会使用微积分。事实上，你们中很少有人会在你们的职业生涯中使用它。" 然后他停顿了一下。"那么你们想知道为什么应该关心吗？"

我们几个人点了点头。

他挑出了班里的一个足球校队队员。"你在一周内经常练习足球，对吗，蒂姆？"老师问。

"是的，"蒂姆回答。"几乎每天都是。"

"你和你的队友们在练习时有没有举重？"

"是的。周二和周四，我们在举重室花了很多时间练习。"

"但为什么呢？"老师问。"在比赛中，你的教练会不会告诉你使用一种战术，需要你给对方做卧推？"

"没有，当然没有。"

"那为什么要举重？"

"因为它使我们更强大。"蒂姆说。

"宾果！！"老师说。"这和微积分是一样的。你在这里不是因为你要在你的日常生活中使用微积分。你在这里是因为微积分是你大脑的举重。"

我从来没有忘记这一点。

I took calculus my senior year of high school, and I really liked the way our teacher framed this on the first day of class. 

He asked somebody to raise their hand and ask him when we would use calculus in our everyday life. So one student rose their hand and asked, “When are we going to use this in our everyday life?” 

“NEVER!!” the teacher exclaimed. “You will never use calculus in your normal, everyday life. In fact, very few of you will use it in your professional careers either.” Then he paused. “So would you like to know why should care?” 

Several us nodded. 

He picked out one of the varsity football players in the class. “You practice football a lot during the week, right Tim?” asked the teacher. 

“Yeah,” replied Tim. “Almost every day.” 

“Do you and your teammates ever lift weights during practice?” 

“Yeah. Tuesdays and Thursdays we spend a lot of practice in the weight room.” 

“But why?” asked the teacher. “Is there ever going to be a play your coach tells you use during a game that requires you to bench press the other team?” 

“No, of course not.” 

“Then why lift weights?” 

“Because it makes us stronger,” said Tim. 

“Bingo!!” said the teacher. “It’s the same thing with calculus. You’re not here because you’re going to use calculus in your everyday life. You’re here because calculus is weightlifting for your brain.” 

And I’ve never forgotten that.