Xueba couples do not study

Chapter 161 I already have the answer in my heart. (plus more)

The next class was relatively simple. Although Lin Sheng appeared to be listening to the class very seriously, she actually didn't listen carefully to what the teacher said.Although some teachers asked her to answer questions suddenly, she could always answer them quickly, which saved her from being punished for being distracted in class.

After the break of the third class, the math class representative came out of the office, turned on the projector and put the paper on it, so that everyone could look at the big screen.

On the big screen, there was a handwritten math problem.

After everyone briefly read the questions, they heard the representative of the math class say: "This is an extended question given to me by Teacher Liu. Students who are capable can do it."

Although everyone screamed in pain under the podium, they still copied the topic and prepared to do it.

During the last chemistry class in the morning, Lin Sheng was writing the extended questions that Teacher Liu had left for them.Although the math teacher said that you should do it when you have time, don't delay the study of other subjects, and this question is also very difficult, students who are able should try to do it.Lin Sheng knew that He Yang would definitely solve this math problem. After all, He Yang's math scores were the most outstanding among the three main subjects. It seems that He Yang will choose science in the future.

Although she is still hesitating whether to choose essays or science in the end, although Teacher Tang and Teacher Zhang suggested that she choose science in the future when she finished the entrance test yesterday, but for some reason she recalled her father and brother The figure of Lin Han working, she wants to help them.

The Lin family's company will be inherited by Lin Han in the future, Lin Sheng knows this very well.

She thought carefully for a long time during the winter vacation, thinking about how to help them and help them take a step forward.

One day, she heard what Lin Han said on the phone with someone, and she already had the answer in her heart.

Although she was discovered by Lin Han at that time, and told her not to consider them when choosing a major in the future, but to consider whether she likes it or not.

Although Lin Sheng nodded in agreement, Lin Han knew Lin Sheng's character well, so he didn't say much. He just looked at her and sighed helplessly.

Lin Sheng looked at the question. It was about polar coordinates and parametric equations. It was something he had just learned in class today. Although the teacher led them to do a few questions in class, it was a bit difficult to answer without fully mastering them. The problem is still more difficult.

Lin Sheng glanced briefly in class, and now he is picking out the main information.

Straight curve cp=2cos, the point on the curve c is shifted to the left by one unit, the ordinate remains unchanged, and the abscissa is twice as long as the original, then the curve C1, the straight line equation (two equations), the straight line l and C1 intersect A, B two points.

The first question is to find the rectangular coordinate equation of C1 and explain what kind of curve it is.

Lin Sheng quickly solved this problem. The answer is x/4+y=1, and the curve C1 is an ellipse with focus (-√3, 0) and (√3, 0) major axis 4.

After solving the first question, Lin Sheng was not relieved, and turned his attention to the second question.

The second question sets the point P (0, √3), and finds the value of 1/|PA|+1/|PB|.

This question seems simple, but it is necessary to find the values ​​of ta+tb and tatb according to Veda's theorem, and the result can be obtained by substituting the algebraic formula required for simplification.

For those who have just learned the theorem and are not very proficient in theorems, this question is undoubtedly not difficult.

Enter the parameter equation of the straight line l into the equation of the curve C1 to obtain an equation, then set the parameters of A and B as ta and tb, and then calculate the values ​​of ta+tb and tatb according to the Vedic theorem, and obtain ta+tb=48/13, tatb=32/13.Then substitute 1/|PA|+1/|PB|=|ta+tb|/|tatb|=3/2
Finally, I sorted out the calculation results and process again, and wrote this problem in a notebook. On the cover of the white notebook, the word 'Mathematics' was written with a black marker, and Lin Sheng's name was directly below it. , it can be seen that this is Lin Sheng's special notebook for mathematics.

Lin Sheng flipped through several pages, and finally found a blank space to copy the question on, and wrote down the steps of solving the question in the notebook with a black carbon pen, and finally wrote the thought of the question with a red carbon pen next to it , After finishing these things, he relaxed and leaned back on the chair, and sighed.

After class, He Yang refused the kindness of his classmates and did not go to play backgammon placed not far behind him. He opened the draft paper that had been left by the teacher in class. The first question had already been solved on the draft paper, and the rest Half of the second question has been solved, and the thinking is very clear, and the rest is to calculate the result.He Yang calculated very quickly, and quickly concluded that the result of the second question was 3/2. After finishing, He Yang looked diagonally ahead of him. Lin Sheng didn't know what he was writing at this time, but He Yang knew At this time, Lin Sheng was also calculating the questions left by the teacher just now.

He Yang kept looking at Lin Sheng. Lin Sheng was so focused on solving the problem that he didn't notice He Yang's gaze. After three or four minutes, Lin Sheng leaned back in the chair as if relaxing.

It seems to be solved.

The corner of He Yang's mouth raised, Lin Sheng looked back for some reason, just in time to see He Yang looking at himself again, He Yang did not avert his gaze, the two's gazes met in the air, and finally He Yang pointed to the blackboard that was already on the blackboard. The math problems that were erased by the students on duty did not make a sound and said the results in spoken language.

Lin Sheng wanted to know if He Yang had solved the problem, but when he turned his head, he found that He Yang was looking at him, as if it had been some time.

Mathematics is still not as good as him.

Lin Sheng sighed, and then saw He Yang pointing to the blackboard, and said a number without making a sound.Lin Sheng immediately thought that what He Yang was talking about was a question from the last math class, and followed the memory just now to judge the number he said based on the shape of He Yang's mouth.

3/2.

Lin Sheng confirmed that the answer He Yang said was not wrong with the answer he got, so he nodded in He Yang's direction.

He Yang knew that Lin Sheng understood the meaning of what he just said when Lin Sheng nodded, and was about to speak again when the class bell rang, Lin Sheng made an apologetic gesture in He Yang's direction, and then turned to look at the blackboard.

The teacher of the next class was already standing on the podium when the class bell rang. After the bell rang, everyone called out to start class. Everyone stood up and said hello to her, and then sat down.

It seems that there is no need to calculate in this get out of class. Let's talk to him/her after class.

This is what Lin Sheng and He Yang are thinking together at this time, deep in their hearts. The 45-minute class made the two of them feel that time passed very slowly, even though the last class passed quickly.

The two stood up together after class, and smiled when they looked at each other. The people in the class didn't know why the two of them stood up and laughed, but they didn't care much, and continued to complete the task in hand.

Sure enough, they all thought the same thing.

　Today, the fourth and fifth updates merged w
　　
　
(End of this chapter)