The freshmen officially started class, and with the care of the dean, Yang Fan continued to follow the progress of the sophomore class.

In the first year, the solution is over, and the sophomore year has to be studied, plus ordinary differential equations, real functions, complex functions, differential geometry, operations research and cybernetics.

The real function is studied ten times, and the functional analysis is cold. When it comes to the middle and late stages of the topology, even the top students have to kneel.

In the first-year mathematics class, Yang Fan often saw his classmates exchanging their experiences in mathematics and asking about course materials.

Mathematics majors in college, there are at least 3 levels of difficulty, Mizuki, the difficulty goes straight to the top.

Yang Fan has already suffered this heavy blow once, and the high and low numbers are really not of an order of magnitude.

If you want to complete the credits, there is basically no problem, as long as you do the exercises explained by the teacher in class and the exercises in the book. If you want to learn thoroughly, you can't have enough energy at 100%.

In the sophomore class, I didn't feel strange about Yang Fan's appearance. At this moment, his identity has changed, and he is no longer a senior in high school, but a world-famous Mizuki scholar.

As the difficulty of learning increased, Yang Fan found a strange question, why the domestic mathematics class spans so much.

Feng Yao also once said that there is a fault in this problem, it seems that there is a fault line from low to high.

Whether or not to translate or compile a general textbook, step by step from easy to difficult.

The more he thought about it, the more he felt that it was feasible. It's just that with his knowledge, he is still a little bit of accumulation, his heart is high, and his ability can't keep up and he is helpless.

The most important thing in front of you is to conquer mathematical modeling. The two people in the dormitory were staring at him at any time, but he worked hard and watched Mr. Mizuki Xie Jin's public class over and over again.

And Yang Fan is also desperately brushing up on the knowledge of modeling, and he can't say where the specific location is, the lack of reference and comparison.

On Friday, September 9th, the National Collegiate Mathematical Contest in Modeling began, lasting for 72 hours.

At this moment, there are at least 20,000 or 30,000 mathematicians looking forward to it. At 8 o'clock, the online question bank will be distributed.

(A) Sun shadow positioning

(B) Taxi resource allocation in the "Internet+" era

(C) Willow tips on the moon

(D) Crowdfunding planning and design

The competition is divided into two levels: undergraduate and junior college, and AB undergraduate topics.

"Brother Yang, what do we choose?" Pan Zhe said.

The direction of the division of labor, the three of them have been confirmed, Yang Fan is considered a temporary commander, and he is responsible for filling in the final paper.

Bao inquired about Pan Zhe's query information and wrote programs, Su Junan mainly focused on graphics and modeling matters, and finally, Yang Fan summarized them.

"What do you think?" The three of them are a group, and Yang Fan doesn't want to be in charge of everything.

"Compared with the question bank of previous years, a practical problem, question B is just divided into categories. I agree with A. Su Junan took the lead in making suggestions, "A is mainly theoretical knowledge, and it is relatively easy to find information. In terms of complexity, I think A can better set off our mathematical background. ”

"Old Su, you are wrong. Pan Zhe objected, "Urban taxis are a big problem, and the emergence of online car-hailing may be the above to find some feasible solutions." Finalists, may be applied to the real world. We major in mathematics to apply what we have learned. ”

The two turned their eyes to Yang Fan, and in the end, it was up to him to decide.

Yang Fan weighed it, the two roommates were right, AB actually didn't matter at all, the grades were still spoken by the modeling paper.

As for solving the problem of taking a taxi, Yang Fan disagreed, the country has countless powers, and the graduated math seniors have a lot of cars, and they don't want college students to end up.

"Pick A, I like astronomy a lot. ”

Yang Fan gave the answer, Su Junan and Pan Zhe didn't nod, they didn't ask nonsense, efficiency first.

Download the question and the ORD file opens.

Question: According to the solar shadow positioning technology, the relationship between pole length, shadow length, latitude and longitude, time and date is established through the law of relative motion between the sun and the earth, and the model is established.

According to the time difference calculation relationship, when the time of the capital is between 9:00 and 15:00, the time of Tianmen Square, and the established model is applied.

The length of the shadow is calculated according to the shadow coordinates, and the function of the time of the capital and the length of the shadow is fitted to find the lowest point of the shadow length, so as to find the local longitude according to the time and determine the possible location.

When the question appeared, Su Junan and Pan Zhe lost their stretches slightly, understanding the content, but they didn't know what they were talking about?

"Where to start?" said Su Junan.

Yang Fan frowned and thought about it, and gave an order: "Brother Pan, search for true solar time, average solar time, declination angle, solar altitude angle, entropy method, as long as you think you can't understand the information downloaded, and mark the keywords, the paper must be famous." ”

Su Ge, analyze the diurnal and annual changes of the angle of the sun's rays hitting the object, cause the length and orientation of the object's shadow to change regularly, and use Matlab software to draw an image of the shadow length with time. ”

The big problem of the sun's shadow positioning is divided into two small questions, and the answer is to be done in four steps.

First, the model assumptions. Second, the use of symbols in the model illustrates, and third, modeling. Fourth, calculations.

In response to the first question, Yang Fan hurriedly grabbed a pen and paper and put forward six hypotheses:

1. Assume that a single light source irradiates ...... 6 Think of the entire sky as a celestial circle.

There are 12 types of definition symbol settings, partial magnetic angle, angle of incidence...... Shadow length.

The most important thing is modeling, setting up the graph, and calculating the model solution.

......

For three days and three nights, none of the three left the dormitory. I asked my classmates to send me directly for dinner.

At 4 a.m. on Monday, Yang Fan finally completed the final step, looking at the 24-page paper on the document, and a sense of pride rose.

The graphics are lush, reasonable, and all kinds of complex calculation formulas are dazzling. didn't use any cheating methods, it was done by the accumulation of knowledge of the three people.

Su Junan and Pan Zhe didn't know when they fell asleep on their desks. The final summary homework was completed by Yang Fan alone, and they couldn't help.

His eyes were bloodshot, his face was stubble, his face was pale, but his brain was unusually excited.

"Wake up. Yang Fan pushed the two.

"What time is it?" Pan Zhe raised his head blankly, the closed curtains and the dormitory lights that had been turned on for a long time made them all lose their sense of time.

"Done?"

Yang Fan nodded, Pan Zhe jumped up happily and screamed: "Old Su, get up quickly, it's over." ”

Dozens of pages of documents, Pan Zhe's slow pull-down like a pilgrimage, sphere graphics, curve graphics, and dense formula calculations all made him intoxicated.

"It's not easy. ”

Su Junan also woke up, leaned behind him, followed the beauty of the paper, turned his head and said, "Brother Yang, don't play these things on your own initiative in the future, the brothers can't stand it." ”

"Brother Su, it doesn't matter if you don't get good grades in your paper. Yang Fan opened the curtains, and the stars flashed outside: "What we enjoy is the process of hard work, don't you think that these three days and three nights will be a wealth in life." ”

The dormitory is quiet.

Pan Zhe scolded with a smile: "Don't pour poisonous chicken soup, come and sign and send it." I'm counting on this paper to win an award, so I can add some credits. ”

The results won't come out until a month later, but the three of them don't care.