YEN-JIE LEE: So during class, I like to take a few minutes of break. So that will allow the students to take some rest, because usually the content is so intense, such that people-- it takes some time for the students to actually digest, and then to understand, the concepts covered in the first part of the lecture. And also, it give them an opportunity to interact with me. And usually, during the break, they bring a lot of questions, which I didn't anticipate before. There are many, many questions about mathematics and those of physics concepts.
Here you have del square e, right? And the del square, you have 1, 2, 3, turn, three operators. And while you are-- if you write everything explicitly-- so basically, this operator is going to be operating on ex, ey, and zz.
And then, we can usually solve them during the class. And I can even cover part of the question asked during the break, so that everybody, actually, can benefit from those interesting questions people actually bring up during the break.