Under her hand was a stack of papers, densely packed with numerical calculus. The little girl is still writing.

"Little girl, what are you doing?" Jiang Xingchen stepped forward and sat next to Nier and asked.

"Ah!" Nier exclaimed, only then did she realize Jiang Xingchen: "Sir, why are you here....... I found something wrong!"

"Oh, what problem did you find, the amount of computation needs to be so large?" Jiang Xingchen asked curiously, picking up the stack of papers under Nier's hand to look at it carefully.

"I've found something strange! If it's an isosceles right triangle, according to the Pythagorean theorem, the length of the hypotenuse would be a strange value!" said Niel.

Jiang Xingchen also saw Nier's calculation clearly at this moment, she was opening the square, but what she opened was an infinite non-cyclic decimal.

"Don't forget it, it's an irrational number!" Jiang Xingchen put down the draft in his hand, he really hadn't mentioned the matter of irrational numbers before, because he didn't know how to explain it. He only vaguely remembered that it could be defined by rational number division, but he had only heard of rational number division and didn't know what it was about.

"Irrational number?" Nier's brows furrowed even tighter, and then asked: "Does an irrational number mean that this number is unreasonable, but it is obviously a hypotenuse, which has practical significance, a line segment must have a specific value, how can it be unreasonable?"

Jiang Xingchen scratched his head, he really couldn't explain this thing, in the previous life, this irrational number had caused a mathematical crisis for more than 2,000 years.

After thinking about it for a while, Jiang Xingchen decided to let the little girl jump out of here first, and she couldn't get stuck here.

"It's a big problem. With your current knowledge of mathematics, you can't solve it yet! Let's look into this again!"

But after Jiang Xingchen finished speaking, he knew that his words were in vain. The little girl didn't listen to it at all, and was still frowning and thinking.

"Nier, the mathematical deduction has to come step by step! There is more to the problem of the figure than the isosceles right triangle...... These days, you've been looking at graphics, so I ask you, if you were given a ruler and a compass, would you be able to make those shapes if I drew them?"

The little girl raised her head and didn't think about it. Nodding his head, he said, "I can make it, and I've already done it!"

Jiang Xingchen saw that he had attracted Nier's idea, and continued: "Okay, now let's make it more difficult! Or use a ruler, a compass, note that this ruler is not marked with a scale! Then can you divide any angle into threes, can you make a square, so that his area is equal to the area of the known circle!"

Jiang Xingchen is talking about the three major problems of ancient mathematics. But he also only remembered two, and there was one more cube product problem that he forgot.

Through Guò's study of this, analytic geometry can be introduced to solve graphical problems using algebraic methods. Of course. Jiang Xingchen didn't want to sue Sù Nier, if Nier could study the eyebrows by herself, it would be really amazing.

Other than that. He also wanted to put this thing out there and let all the children study it together. It would be even more perfect if you could find someone who shares the same heart as Nier. In the last life. The formation of a mathematical system is by no means something that can be done by two people. Although there is such a plug-in as him in this life, it is quite difficult to rely on Niel herself.

"Okay, I'll try to solve these two questions first!" Nier was very interested in doing the problem, and nodded with a smile at Jiang Xingchen.

"Little girl, do you think my question is very simple?" Jiang Xingchen patted Nier's head.

"Look...... It doesn't seem to be difficult!" Nell said.

"Okay, then you can solve it and try it!" Jiang Xingchen said and stood up, and at a glance he saw the pile of scratch paper made by Nier, and a flash of inspiration suddenly flashed in his mind.

"Study hard, I'll give you a gift when I go back!" Jiang Xingchen said.

"Ah, the lord wants to give me a gift, what is it...... Isn't it a good meal?" asked Niel, happily.

"Snack goods! If you really solve these two questions, I'll make you a big meal!" Jiang Xingchen raised his hand and scratched the little girl's nose.

"What the lord said, don't go back!"

"I will never regret it, but the gift I gave you is not food! you will know when you turn around!" Jiang Xingchen said and waved his hand and walked inside.

Niel said goodbye to Lord Sir with joy, and instead looked down and began to study the two graphic questions......

Entering the room, Xian Ning was also writing and painting at the desk, and it could be seen that he was very engaged, and he didn't react to Jiang Xingchen's arrival.

"Xian Ning, how is the research?" Jiang Xingchen asked.

"You're here!" Xian Ning raised his head, put down the pen in his hand, and sighed: "The steam locomotive has too many parts, and the boiler needs to be horizontal to increase the heating area......! The main problem is the brakes!"

Jiang Xingchen shook his head helplessly, and he didn't know the braking system of the steam locomotive. This can only be studied a little bit.

"Xingchen, it's not easy for you there, you still have to hold on to the mold and lathe!" Xian Ning said.

"I know that this is just the beginning, and I will have to train maintenance workers in the future. A railway requires a lot of people to maintain...... Okay, you can study it first! I'll go back!"

Jiang Xingchen turned his head and walked two steps, suddenly stopped, and said, "By the way, I have something for you when I turned around, I thought of it when I was guiding Nier just now!"

"What is it?" Xian Ning asked.

"I'll tell you when I make it, I have to learn this thing for a while before I can use it!" Jiang Xingchen said with a smile.

"I'll have to study for a while, so let's wait until I develop a steam locomotive, I really don't have time now...... And the flat glass hasn't been figured out yet...... Construction on the ground has already begun in Duanjia New Town, and you are asking for glass windows!"

Jiang Xingchen smiled bitterly, when the new city was being built, he thought about going one step closer and installing glass windows! But now there is no progress in flat glass! The main reason is that tin has not been found, so it is impossible to carry out float production.

"That's also something that can't be helped, what should we do if we can't be busy now!" Jiang Xingchen sighed, there were still too few talents in the territory, thinking about the construction of the new city and the use of paper paste windows in the buildings, he felt like he had been struck by lightning.

"Let's take a look after a while, when the university is completed, we will start recruiting students, hoping to have good seedlings. Jiang Xingchen sighed.

"Xingchen, I patronized the car and glass just now, and I forgot about business!" Xian Ning put down the pen in his hand, stood up, and asked, "Can the magnifying glass you designed be bigger?"

"This ...... But it takes a lot of trying, and we don't have time right now!" Jiang Xingchen replied. If Xian Ning talks about telescopes, this is simpler. But microscopes are different. Although both have two sets of convex lenses, an objective lens and an eyepiece, the microscope is much more elaborate and requires multiple realizations.

"There's no rush about this, just remember it...... You're really good, how did you figure out the magnifying glass?" Xian Ning asked with a smile.

"Hehe, you don't know me yet, maybe a strange idea will come up at some point!" Jiang Xingchen said casually, turned his head and ran away.

Xian Ning shook her head: "Every time I ask this question, I run ......"

Back at the lord's mansion, Jiang Xingchen immediately ordered his subordinates to find wood, and began to make zuò with a carving knife. After a while, a rectangular frame came out, and then the holes were drilled to make beads one by one......

What Jiang Xingchen makes is an abacus, a calculation tool that has been used from ancient times to the present in the previous life, even when modern electronic products are flying all over the sky, there are also abacus. He had only come up with it after looking at Niel's pile of calculations.

With an abacus, the calculation of the four operations is faster, and in the last life, it is said that the master is faster than the calculator.

With this abacus, it is much faster in financial accounting, which is definitely a super blessing for Grandpa Fu.

Jiang Xingchen's idea is to push the abacus into the classroom, more than a thousand children. Different talents, different personalities, different preferences, it is impossible to enter the research institute, and in the future, you will definitely have to enter various positions, and learning abacus is equivalent to cultivating talents for the future financial department.

"Boy, what are you doing here?" When Jiang Xingchen was busy with his work, the old man came to the courtyard.

"What a fun thing!" Jiang Xingchen turned his head, smiled at the old man, and said, "Do you want to try it?"

"Don't!" The old man didn't stun his head, and said loudly: "You kid wants to yin me again, don't you have a good mind when you smile!"

"Cut!" Jiang Xingchen pursed his lips and said disdainfully: "You want this thing, I can give it to you!

Kong Ming's lock has been unlocked, and you still want to stump me!" The old man smiled proudly, as if he saw Zhao Danqing and the second child sweating profusely.

"Hmph, you also called it unraveling? Don't put gold on your face, tell you, there are more types of Kong Ming locks, all kinds of them. I only gave you twenty-four sticks that day, if you want to try it, I'll make you forty-eight when you go back!"

The muscles on the old man's face trembled twice, and a black thread hung down, but he didn't want to suffer that kind of torture anymore.

Jiang Xingchen continued: "In addition to Kong Ming's lock, I have a more fun and more difficult one! It's called the Rubik's Cube, if you're interested, I'll make you a fifth-order one when you go back, it will definitely make you feel refreshed!"

"Forget it, forget it!" the old man hurriedly waved his hand and said, "These things you said, let's talk about them when I want to be clean for a while one day!"

Jiang Xingchen smiled and asked, "Didn't you learn Tai Chi with Miss Tang, why did you have time to run out? Haven't you heard of Tai Chi not going out for ten years, you are so unconscious, and Miss Tang doesn't care about you?"

Jiang Xingchen counted them all, and surprisingly the old man didn't refute, but his eyes shrank, revealing a wry smile, and sighed: "Boy, don't mention it! I'm afraid I won't be able to learn this Tai Chi ......" (to be continued......

PS: The third watch is over!