Chapter 146

Gu Lu stood back on the podium.

He rolled up the cuffs of his shirt and tapped his fingers on the blackboard, "Everybody look ahead." ”

"The two solutions of Bi Qi and Bai Yao, although they have different ideas, the results are correct. Gu Lu pointed to the dense mathematical formulas on the blackboard and said.

Next, I will explain the solution of these two students in detail. ”

"Let's take a look at the solution steps written by Bi Qi on the left, this is a more conventional Taylor expansion method of solving, the advantage is that it is relatively simple and crude, as long as it is set into the template for calculation, but there are also disadvantages, that is, the operation is complex and easy to make mistakes. ”

In short, it is to convert the function in the problem into the form of Poisson integral and solve the calculation. The computation will be slightly less, but not every problem that Tate expands can be converted into Poisson integrals. Therefore, the solution is not universal. ”

Gu Lu picked up the chalk and circled the two formulas, "Bi Qi's solution, there is no major problem, but there are still a few minor problems." For example, when discussing |x|<1, this formula, and this formula, is completely unnecessary. ”

Since the Taylor series is closed and converges consistently at f(x), the result 2ln|x|∫ can be obtained directly by calculating the (π,0)lnx(1-2xcosθ+x^2)dθ. And here, just replace θ=π-t as a variable, so you don't have to be so troublesome. ”

Under Gu Lu's revision, the original solution formula of more than 20 lines was reduced to more than a dozen lines.

Moreover, Bi Qi's steps, which originally seemed extremely complicated, instantly became concise and clear.

Of course, this is for those students who don't understand what they already read.

As for those classmates who were already confused, they are now even more blindfolded.

Isn't that easier, I don't think so!

Can anyone tell me what exactly the formula for step 3 means?

What should I do if I am swollen, and I can't understand what I should do if I am swollen at all?

Shouldn't I come to Yan University to study mathematics?

Many students doubt themselves.

Zhang Zhenzhen, who was completely blindfolded, looked at Bi Qi who nodded frequently while listening to the next side, and then looked at Ma Zhengxuan, who looked up at the blackboard from time to time, and then lowered his head and recorded something quickly in his notebook, and there was a feeling of doubting whether they were the same kind of people.

"Can you understand?" asked Zhang in confusion.

"It's very basic, why can't you understand it?" replied Bizzie, "Is this difficult?"

Zhang Zhenzhen: "......"

Big guy, excuse me!

Although everyone has done a preview in advance.

But the problem in front of you, for normal people, is probably not the level of difficulty that can be understood by just previewing.

It was used as the finale of the final exam, and Zhang Jinzhen didn't feel that it was too much.

But just now, Bi Qi and Bai Yao both came to the stage to make this question.

And the two of them used two different ideas and two different solutions.

Fancy problem-solving!

This is not a show of strength, but it is enough to be called a show of skill!

Zhang suddenly doubted himself again.

We...... Is it really the same kind of people?

is also a Yan University student, known as a scholar-like existence, and the level is also divided into three, six, nine and so on.

Obviously, in their class, Bi Qi, Bai Yao, and Ma Zhengxuan are the top ones.

The rest of the people can only look at it.

But who is also a top student, who is willing to be behind.

After seeing the strength of Bi Qi and the others, many students in the class have secretly made up their minds and vowed to surpass a few others.

Anyway, there is still a long time before the final exam.

They have plenty of time to achieve corner overtaking.

............

Gu Lu also considered that only a very few students might be able to understand his explanation, so he directly and quickly brushed over the last question.

"Well, that's it for the two solutions to this problem. It's okay if you don't understand it now, but if you don't know how to do this kind of question at the end of the semester, then I'm going to talk to you about it. Gu Lu smiled and looked at the people below, his eyes were peaceful.

But there are still many people below who shrank their necks and nodded in fear.

They have just entered college in high school, and they have obviously not yet come out of the fear of teachers in middle school.

Gu Lu smiled and didn't care.

It is a good thing that the teacher has majesty in the eyes of the students, he does not deliberately demand himself, and he must mingle with the students.

Just as Gu Lu opened the textbook and was about to start lecturing, a male student below suddenly raised his hand and asked, "Teacher, is the solution given by Bai Yao already the simplest solution to this problem?"

"You mean the fourth question just now?" Gu Lu pointed to the question on the blackboard that had not been erased.

The boy nodded heavily, "That's right." ”

"Is it the simplest solution?" Gu Lu shook his head with a smile and replied, "Not really. ”

Gu Lu spoke, "The simplest solution to this problem only requires six formulas!"

Hiss——!

The sound of gasping cold air rang out below.

Six...... Six formulas!

Such a complex problem can be solved with only six formulas?

Just kidding!

The classmates' eyes widened and they looked at each other in disbelief.

I thought that Bai Yao's eighteen formulas were concise enough, but in Teacher Gu's mouth, they didn't seem to be worth mentioning.

Six formulas, what can be done.

Light is a function deformation, integral solving, these are two formulas.

Teacher Gu won't be scolding them!

"Teacher, can you tell us about it?" Bai Yao's eyes flashed, and her voice was soft.

"It's okay to talk about it, but I guess, it's hard for you to say that you can understand it. Gu Lu shrugged, turned around and wrote six formulas on the blackboard.

[Let g(x) be a single-valued function determined within the region D, and x0∈ D, limg(x)-g(x0)/x-x0 is equal to a finite complex number α...... It can be obtained, ∫ln(1-2xcosθ+x^2)dθ=2πln|x|. 】

Six formulas, one is not much, and one is not much.

The students all looked up at the six formulas, looking confused.

What's this?!

Originally, Bi Qi and Bai Yao's steps, they could still understand a little bit while they were alive.

But now the solution given by Gu Lu is really incomprehensible to a line of formulas!

Every number symbol, they know.

But when they are connected, they can only look at each other without words, you don't know me, I don't know you at all.

Not only the other students, but even Bi Qi and Bai Yao were also in a completely confused state.

Only Ma Zhengxuan, touching his chin, looked at the steps written by Gu Lu, and pondered slightly.

On the podium, Gu Lu smiled, "It's normal that you can't understand it." ”

Because, the knowledge theorem used in it is the content of "Complex Variable Function". Gu Lu looked at everyone in the audience with a smile, "That's a course you only have to learn in your sophomore year." ”

............

PS: Two chapters are released together today.