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Chapter 174 Butterfly Theorem (seeking monthly ticket subscription!)
According to Lin Dong's level, the first ten steps are quite perfect without any mistakes.

But when the No.11 step came out, the meaning of the existence of that auxiliary line became a curve, and it was two curves folded in half.

This means that if Lin Dong takes this line as a breakthrough, he will be trapped on this curve forever, and it is difficult to get out, even if there is enough time in the IMO event, but he will make a mistake on this step If this happens, the delay will be very long. The national team has lost consecutively in the IMO competitions in the past two years and has not won the national team championship. The coach will have unshirkable responsibility.

For Lin Dong, he was disappointed.

ruled out.

The few remaining players are not enough to compare with Fang Chao, Zhang Tiannan, Xiao Zizhan, and Jin Zixuan, and they still lack something.

Fang Chao also shook his head. He was impressed by Lin Dong's words. He has good talent and ability. He even got higher scores in the previous assessments.

But how to put it, it is like a car, a car with good performance. If it is modified and replaced with a powerful engine, then although this car will not reach the level of a supercar, it will be a semi-supercar. No problem?

But Lin Dong didn't have the mentality to advance aggressively, and was too well-behaved, which was a fatal weakness for math competitions.

Although the things that IMO emphasizes are all within the scope of high school, over the years, every year the competition has been making breakthroughs, seeking changes and innovations.

If you still stick to the old routine, you will be eliminated eventually.

So in Fang Chao's view, Lin Dong is basically out of the top six, because judging from these players, the players that Professor Lin called up are basically his favorites by default, but if this level cannot pass , then unfortunately, after more than two months of hard work, you still failed to reach the national team.

Zhang Tiannan understood at the No.14 step.

Jin Zixuan reacted at No. 15 steps.

Xiao Zizhan's words came to him at the No.17 step.

As for the others, they are still watching Lin Dong answering, and have not found anything wrong so far.

Among the players whose eyes fell on Professor Lin, there was only one Fang Chao who satisfied him the most, but if it was only this one person, it was difficult to be the leader alone. The six members of the national team need strong soldiers. Only in this way can they lead the team. The national team goes to victory.

As for Zhang Tiannan, Jin Zixuan, and Xiao Zizhan, they are pretty good. At least they have come to their senses. If they sharpen their skills, they may not be able to become powerful weapons for the country.

"Professor... I... I can't do this problem anymore..."

Professor Lin said, "Okay, Lin Dong, you go down first."

Professor Lin didn't look at the four people who were basically confirmed, because it was unnecessary, and his main purpose of this question was to select the remaining two.

"I'll give you two more minutes..."

Before Professor Lin finished speaking, one of the female contestants weakly raised her hand and said, "Professor, I want to try."

"Oh?"

Professor Lin was stunned for a moment and then said, "Chen Qin, come up and try."

"Yes, Professor."

Chen Qin is about 1.6 meters tall, and her body is a little fat. But after two months of morning exercise, the so-called obesity has now become a little stronger. She wears a pair of 525-degree polarized glasses above her eye sockets.

At this time, she walked up to the stage, picked up a piece of chalk, and then asked, "Professor, can I erase part of Lin Dong's answer and keep part of it?"

"can."

Professor Lin gave Chen Qin this authority.

Now that the training camp is coming to an end, almost all the things that should be taught have been handed in, and the rest depends on the free play of the players.

Chen Qin received the order and directly erased most of Lin Dong's answers with a blackboard eraser, leaving only the first ten steps. Then she drew a symmetrical triangle in the concentric circles.

Butterfly Theorem!

Look, isn't this a beautiful name?

And its existence provides a lot of effective help in mathematics.

And it also has a Chinese name, that is the butterfly theorem.

The butterfly theorem is one of the most wonderful results in European plane geometry. This proposition first appeared in 1815 and was proved by Horner. There are countless proofs of this theorem, and it is still studied by mathematics enthusiasts. There are various changes in time.

Mathematics itself is ever-changing, so if you want to solve a problem, you must find the corresponding steps.

When the Butterfly Theorem came out, Professor Lin knew that Chen Qin would be the fifth player and the first female player in the national team.

When this thing came out, Fang Chao knew that Chen Qin knew how to go about this problem.

Thousands of roads lead to Rome, but to use the knowledge of high school students to solve the problem that Professor Lin put on the blackboard, other methods are difficult to work, and many detours are required, and this may not be possible. Don't look back at the south wall, but if you use the butterfly theorem, then many things will be logical.

As long as anyone can think of the butterfly theorem, the difficulty of this question has plummeted, but how many people can think of the butterfly theorem?It is so beautiful, so beautiful that people only notice its beauty, but ignore its danger.

"That's what it is!!!"

"It's actually the butterfly theorem!!"

"If I had guessed that I used the butterfly theorem, this question would not be difficult for me at all..."

"Ah, ah, why can't I think of it?"

"Professor Lin didn't let Fang Chao and the others get up to answer the question because he used it to test us. Whoever can figure it out will basically be sure that a place will be awarded. Chen Qin, he will be the winner this time." Fifth player."

Lin Dong stared blankly at the blackboard where Chen Qin was answering with the butterfly theorem. The characters and mathematical symbols on the blackboard became beautiful under the butterfly theorem. A projective method allowed Chen Qin to perfectly This problem is solved.

If you tell Fang Chao the difficulty of this question, it will only have 2.5 stars. This is a question with a very low score, because it is not difficult, as long as you master the skills, even for Fang Chao, it is almost impossible for Professor Lin to solve this question. It's just a sub-question, but it's a pity that he can't give hints, otherwise, countless contestants will be selected for such a simple question.

The significance of Professor Lin's question is lost.

(End of this chapter)