I just want to be a quiet scholar

Chapter 40 Three Methods
Shen Qi took the blank sheet of paper handed by Secretary Liu: "Alright, I'm a newcomer, so I'll do the quiz first to suppress my shock."

"Give you 1 hour, I'll go out for dinner." Officer Liu stood up and looked at his watch. It was almost five o'clock, and it was almost time for dinner.

"I'm really hungry too." When it came to eating, Shen Qi was indeed hungry.

"You will be allowed to have dinner after completing this question within the specified time and the answer is correct." Secretary Liu said with a blank expression, and added: "This is the first rule of the Olympic National Team."

"Guan Liu, you are not legally allowed to treat minors like this!" Shen Qi strongly protested, he was not allowed to eat if he couldn't solve the problem, so cruel, we are a socialist country with the rule of law!This shock was too shocking to hold back.

"Shen Qi, you are a gold medalist in a math competition and a national champion, not an ordinary minor." Director Liu was not soft-hearted at all. He pointed to every corner of the office of more than 20 square meters: "In the process of solving problems , you can consult any mathematical literature in this room, many of them are not for sale, and the Chinese Mathematics Association obtained them through special channels. You should feel lucky, because you are swimming in the ocean of knowledge."

"I came to your great capital as a high school student from another area. I have no relatives, no friends, no friends. What can I do? Mr. Liu is what you say. You are a boss. I can only submit." Shen Qi had no choice, he are vulnerable groups.

Secretary Liu left, leaving a cold back.

Shen Qi pulled a chair and sat down, spread the white paper in his hand on the table, and carefully reviewed the questions on the paper.

The first thing that catches the eye is a simple pattern, a straight line running through an ellipse, like a squashed "Sun" character.

在“日”字的12点、3点、9点三个方位，分别标注y(x)、x2、x1。

Below is the text description:

"According to the above figure, the unknown function that appears in the integrand can make the integral reach the maximum or minimum value. The concrete description is the shape that the rotating surface must have with the axis moving at a constant and making the motion resistance minimum, then its mathematical What is the description?"

The question is not complicated, everyone can recognize the graphics and the Chinese characters, but it can be conservatively estimated that more than 99% of high school students in China do not know what this question is for Laozi?

"Hehe, hehehe." Shen Qi smiled, like a fool.

He smirked because it was time for dinner.

This question is not difficult. For Shen Qi, a one-sentence summary is: use mathematical language to describe simple physical movements.

This requires the answerer to have a relatively deep mathematical knowledge reserve, and the physical knowledge reserve to the scope of compulsory high school textbooks including Newton's three laws is enough.

Shen Qi answered with a pen, and wrote his mathematical description on this A4 piece of white paper.

The simple point of this question is that Secretary Liu threw a ball on the lake, the ball jumped on the lake, and finally floated on the lake. Please explain this common phenomenon in mathematical language.

Shen Qi used Euler's steepest line theory, that is, the integral is replaced by the finite sum, and the derivative in the integrand is replaced by the difference quotient.

This not-so-esoteric theory is extremely widely used, and its role is to formulate the integral as a function of a finite number of coordinates of y(x).

Shen Qi drew an arc on the white paper with a very simple technique.

This operation is not difficult, and it can be done by engineering students who have scored [-] to [-] points in the online test.

Shen Qi's operation continues, and by making the variation of the integral equal to zero and transforming the resulting difference equation with a rough limit process, he obtains the conditions that must be satisfied by the minimization arc.

Shen Qi's answer was written on one side of the A4 white paper, and it was done.

Looking at the time, only 15 minutes had passed, and Mr. Liu had not returned yet. Shen Qi was also idle when he was idle, so he turned the A4 white paper over and continued to write.

This time, Shen Qi's operation is a little more complicated, making the integral maximized or minimized, not necessarily a bad quotient.

Euler's method is only entry-level, and Lagrange's method is advanced.

Shen Qi traced a crescent moon on white paper, and deduced the endpoint conditions that must be satisfied by the minimization curve with changing endpoints. This process is quite tortuous.

After 20 minutes, Shen Qi gave a second mathematical explanation.

Seeing that there was still time, Shen Qi took a new piece of white paper and began to deduce the third mathematical explanation.

At [-]:[-], Shen Qi was really hungry. He put the pen on the table and unzipped his backpack to find something to eat: "Why didn't Mr. Liu come back, let's have a chicken leg first."

After tearing open the sealed package, Shen Qi ate chicken thighs, and he walked around the office while eating.

"This is indeed an ocean of knowledge. There are a lot of books, and some documents can't be seen outside at all."

"Opera-Omnia, L. Euler... What the hell is this, a book in English... Hey, wait, I seem to know the author, Euler, this is Euler's book... Damn, I can't read it in English. I understand, get another one."

"My sister is thirsty...Anna Lai is thirsty...Damn it, this book is even more conspicuous. It's a French book! The author is... Lagrange. I can't read all the French, so please change it."

"Halo... There is also a Russian version of the literature... Secretary Liu is a foreign language expert? There are not many Chinese mathematics literature in this room."

Shen Qi was stunned. Officer Liu's office was a sea of ​​mathematical knowledge, but there were not many books he could understand, and Officer Liu's collections were almost all references in foreign languages.

Shen Qi is very interested in the reprints of Euler and Lagrange's mathematical works. This precious mathematical literature cannot be bought in bookstores or Taobao, unless it is overseas.

However, no matter how interested you are, it is useless if you do not understand foreign languages.

"Should I upgrade my English?" Shen Qi stood in front of a wall of books, nibbling on the braised chicken legs, lost in thought.

At this time, Secretary Liu came back. He was very dissatisfied when he saw that Shen Qi was not burying his head in the questions but nibbling on chicken legs: "Shen Qi! Who allowed you to eat chicken legs? It violated the team rules on the first day when you came to the national team to report. Your organizational discipline is too bad!"

"I'm hungry, I'm growing, Secretary Liu!" Shen Qi shouted innocently.

Secretary Liu said loudly: "Hunger is not a reason, it is far more tragic to die of stupidity than to die of starvation! The chicken legs are thrown away, and you are not allowed to eat until you finish the task!"

"Tyrant!" Shen Qi shouted, he reluctantly threw half a chicken leg into the trash can, and whispered: "Tyrant, dark tyrant..."

"Hey, that's not right! I've clearly finished the problem that Mr. Liu asked, so why throw away the chicken legs!" Shen Qi suddenly woke up.

"Aren't you going to tell me when you're done?" Officer Liu walked to the desk and looked down at the blank sheet of paper with the title written on it.

"I'm starving, I've lost my mind, and I shouldn't be level 5 to play Dark Tyrant." Shen Qi squatted on the ground and sulked. This is the chicken leg that my dad bought for me. dad.

"What dark tyrant is messing around?" Secretary Liu frowned and continued to review Shen Qi's answer: "Euler's second-order ordinary differential equation, if you got it right, you can give this answer within 1 hour, which is quite satisfactory."

"Humph..." Shen Qi lowered his head and hummed in a sullen voice.

"Why are there words on the back?" Secretary Liu turned the white paper over and was instantly surprised: "Lagrange's indefinite integral formula, Shen Qi...you...you used two methods to answer this question I asked. ...within an hour?"

Secretary Liu covered his heart with his left hand, sweat dripping from his forehead.

"Hmph... There is a piece of paper next to me." Shen Qi squatted on the ground, lowered his head, and used his fingers to write out of thin air on the ground, and the word "miserable" was written.

"You... Shen Qi... actually use the Bernoulli Divergence Series... You used three methods to answer the question I asked, within... within an hour?" Secretary Liu gasped, unable to speak well. asked.

"Who can be worse than me, you can only do questions and not eat." Shen Qi muttered to himself.

Boom!
A muffled sound.

Officer Liu fell to the ground with a bang.

"What the hell?" Shen Qi raised his head suddenly, and found that Secretary Liu was lying on the ground, twitching violently.

"Officer Liu, what's wrong with you? You must not die!" Shen Qi rushed to Secretary Liu, stunned.

Secretary Liu's hand trembled and pointed to a corner of the office: "Quick...Go get it...Quick effect...Save the heart pill...In the briefcase..."

(End of this chapter)