scratch Scratch is a program that you can download for free cs50 net and you will see in problem set 0 0 which will be posted on CS50.nettonight under problem sets in both standard and hacker editions, can you do the--can you--it will walk you through the process of getting this software.

你可以免费下载,今天晚上我会在0,放上习套题,这个习题集有两个版本，习题集可以指导你,如何下载这个软件。

哈佛公开课 - 计算机科学课程节选

So, the point is whenever you have derivatives with something over dt, do not hesitate to cancel the dts This will be actually true as long as both quantities are vanishingly small.

关键在于,只要你推出的式子分母上有dt,不要犹豫,直接约掉,这个式子只在,两遍都是无穷小的情况下成立

耶鲁公开课 - 基础物理课程节选