Chapter 121： problem solving

The Higher Education Club Cup is the first place in the National Mathematical Contest in Modeling for College Students.

Zhu Chen's "low-key" appearance made the three team members stunned.

Why can he use such a flat tone and say such savage words?

Zhang Lei said with emotion: "Mr. Zhu, then you are really amazing!"

Zheng Tianyu said in agreement: "+1."

Lu Zhou nodded in approval.

"No, no, it's just a simple competition. You must know that there are people outside people, there are heavens outside the world, my level is not worth mentioning, and the principal is the most powerful." Zhu Chen said modestly, with admiration. He looked at Chen Hao.

Chen Hao's name has become famous in the American academic circle, the real it god!

The kind that can hang up and hammer him!

In the eyes of the great god, the digital-analog competition that Lu Zhou and the three of them were waiting for was just a small test, which made them feel bad.

Moreover, listening to Zhu Chen's words, the principal's programming ability is actually stronger than his? ?

Chen Hao watched the three of them pay attention to him, and said with a hahaha: "Hahaha, don't listen to your nonsense teacher Zhu, I'm a chicken and a dish."

"You guys have a good chat, I'll go first."

After speaking, Chen Hao said goodbye and slipped away.

There were four Zhu Chen left at the scene.

Zhu Chen glanced at the three of them, thought for a while, and said, "Well, let's set up a WeChat group chat face-to-face. From now on, you will need at least 2 hours of training every day. As long as you are free, you can make an appointment here directly after class. ."

"OK."

A WeChat group chat was established, and Zhu Chen changed the group nickname to "Guanghua University Digital and Analogue Contest Team".

Zhu Chen backed up the names of the three and asked, "Are there any reference books?"

Zheng Tianyu and Zhang Lei shook their heads. They were about to buy books today, but they were delayed when the principal called over.

Zhu Chen looked at Lu Zhou again, the other party raised his hand and said, "I have it."

"How many books are there? "Mathematical Modeling", "Mathematical Modeling Algorithms and Applications", "Mathematical Modeling Basic Course" all three?"

Lu Zhou nodded and said, "Yes."

"Well, these three books are basically enough." After Zhu Chen finished speaking, he asked Zheng Tianyu, "Zheng is in charge of programming, right? There are four most commonly used software in the Mathematica competition: Mathematica , lingo and SAS, will any of these work?"

Zheng Tianyu's face flushed slightly, and he said embarrassedly, "It will only..."

Zhu Chen smiled and comforted: "How much language you master is not the key, the most important thing is to be able to use it flexibly and solve practical problems."

Then, when his eyes finally fell on Zhang Lei...

"Can you write essays?"

"Will not……"

"Have you never written a paper??"

"No……"

"..."

The deviations brought by the first two classmates made him think that all three of them would order.

Good guy, there is a salted fish hidden!

"In the past few days, after you have figured out the basic framework of the paper, go to CNKI to download the paper and take a look. If you don't understand anything, ask me when you don't understand. Does CNKI know?"

Zhu Chen explained to Zhang Lei helplessly, until the end, he did not forget to ask again. He was really afraid that Zhang Lei would say, What is CNKI?

Zhang Lei replied embarrassingly, "I know, I understand."

"Well, I have a general understanding of your situation." Zhu Chen walked up to the podium and looked at everyone and said, "I will give a simple mathematical modeling example, not only for Lu Zhou, but also for the other two. try."

After speaking, Zhu Chen turned around, picked up the chalk and started writing.

"Example: When a chair is placed on the ground, it usually only has three feet on the ground, which makes it unstable. However, it only needs to be moved a few times, and the four feet can be placed on the ground at the same time, and the four feet are connected in a rectangle. Model and explain."

After he lost the chalk, Zhu Chen clapped his hands and said with a smile, "Come on, there are pencils and paper on the table, let's move."

Lu Zhou was quietly looking at the title on the blackboard, like a statue, motionless.

When Zhang Lei saw the title, he immediately felt that sitting was a torment.

He looked left and right, finally approached Zheng Tianyu, and asked in a low voice, "Old Zheng, can you do this question?"

Zheng Tianyu thought about it for a while and replied, "It's okay, it's a bit difficult, I have to think about it."

"Why can't I do it..." Zhang Lei stared at the boss, but he still didn't have a problem-solving idea in his mind.

Zhu Chen noticed Lu Zhou's expression and asked curiously, "How is Lu Zhou thinking?"

"Teacher, can I write on the blackboard?"

After Lu Zhou finished speaking, he stepped onto the podium with Zhu Chen's permission.

The chalk turned into an afterimage on Lu Zhou's hand, and it didn't even have time to pause, just waved and wrote.

"untie:

1. Model assumptions:

1. The four legs of the chair are the same length. The contact between the legs of the chair and the ground can be regarded as a point, and the line connecting the four legs is rectangular.

2. The height of the ground changes continuously, and there will be no discontinuities in any direction. The ground can be regarded as a smooth surface.

3. The ground is relatively flat, so that the chair has at least three feet on the ground in any position. "

"Second, build a model:

A Cartesian coordinate system is established with the median line of the initial position as the coordinate axis, and the angle of the chair's rotation around the center O is used to represent the angle of the chair's rotation. The position of the chair can be determined by:

f(θ) is recorded as the sum of the distances between points A and B and the ground

g(θ) is recorded as the sum of the distances between points C and D and the ground

"..."

The steps of mathematical modeling must first make assumptions about the model, then start to propose a model, and the last step is to solve the model.

It's just that when Lu Zhou was still writing the second step, Zheng Tianyu and Zhang Lei below were already dumbfounded...

Zheng Tianyu is fine, he can barely understand.

And Zhang Lei...

He opened his mouth wide, then closed it and opened it again.

The whole person has been stunned.

"How long has it been... This classmate Lu Zhou..."

Before Zhang Lei finished speaking, Zheng Tianyu on the side continued with a solemn expression, "It's amazing!".

Seeing that Lu Zhou's problem-solving has reached the third part.

"Three, model solution:

Let h(θ)=f(θ)-g(θ)

If f(0)g(0)=0, the conclusion is established

If f(0) and g(0) are not 0 at the same time, you might as well set g(0)=0, f(0)>0, after the chair is rotated 180 degrees and CD are interchanged...

……

……

Finally, because f(θ0)g(θ0)=0, so f(θ0)=g(θ0)=0. "

"Clap clap clap!"

Zhu Chen, who was beside him, watched Lu Zhou finish writing in one go, and couldn't help applauding and saying, "Yes, the problem-solving is perfect."

"Lu Zhou has a solid foundation in mathematics, and both Zheng and Zhang need to learn."

Zhang Lei asked Zheng Tianyu beside him, "Do you understand?"

Zheng Tianyu said with some difficulty: "I barely understand 80%."

Zheng Tianyu and Lu Zhou's math abilities differed by 10 points, and it was difficult to understand 80% of them.

As for Zhang Lei, who was 15 points behind, he was a little confused even when he solved the problem.

After Lu Zhou sat down, Zhang Lei turned his head and asked:

"Student Lu Zhou, how did you come up with this question?"

Lu Zhou raised his brows and asked curiously, "Is this problem difficult?"

Zhang Lei was stunned for a moment, and subconsciously said, "Isn't it difficult...?"

Lu Zhou said as a matter of course: "It's not difficult, after doing a mental calculation, the answer will come out."

"..."

"Hush!!!"

Hearing what the other party said, Zhang Lei instantly took a breath!

Also admitted to Guanghua University, why is there such a big gap between people?

He has begun to doubt whether he entered Guanghua University or Tsinghua University!

ps: Ask for a recommendation ticket for a reward! One more chapter!

Thanks to the book friends for the rewards of "The Promise of Life is the Same as the First Time", "Mu_he", "The Light of Morning Dreams", thank you!

I ate a hamburger takeaway tonight, it was a heinous crime...

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