"What is it?" Natalie opened the box curiously and took out a silver bracelet with a small squirrel hanging on it and a string of mathematical symbols.

"Why squirrel?" She was a little confused. She held the bracelet between her eyes and cast a questioning look at Lu Qiujian, "And what does this string of symbols mean?"

"This kind of thing is interesting when you guess it yourself!" Lu Qiujian shook his finger to indicate that he would not tell her the answer directly, "but I can give you a hint, what do squirrels like to eat the most?"

"Nut! (Nut, the pronunciation is very similar to Natalie's nickname Nat)", Natalie immediately reacted, "Oh, Lu! You bad guy!" Squirrels like nut, and her name is Nat, so

The meaning of this bracelet is very clear.

"Ngo! You guessed it right!", Lu Qiujian snapped his fingers to celebrate, looked down at Natalie's eyes, and in her eyes Lu Qiujian saw a hint of shyness, a hint of tenderness, and of course nothing less.

The pounding heartbeat after being hit in the softest part of the heart; after waiting for a while, Lu Qiujian pointed to the string of symbols and said, "Go on, guess, what is this?"

"Um, it seems to be a mathematical formula? r=a(1-private nθ)?" Natalie is also a top student at Harvard. Although she majored in psychology, she is also familiar with mathematics. She quickly saw that

The origin of this string of symbols is known; but what is this formula specifically? Since squirrels mean that they like nat, then this string of formulas also has a special meaning, right?

"Absolutely correct!" Lu Qiujian applauded and asked the waiter to borrow a pen and paper and handed it to Natalie, "In addition to using formulas to express equations, they can also be expressed as diagrams. You can use this formula in extreme

Draw it on the coordinates and see!”

Polar coordinates, like rectangular coordinates, are reference systems introduced to represent the position of a point in space; rectangular coordinates use the distance and positional relationship between the point and each coordinate axis to determine the coordinates, while polar coordinates use angles

and distance represent points, in dealing with certain problems

It would be simpler to use polar coordinates. For example, in Cartesian coordinates, the standard equation of a circle with the center at the origin is x^2+y^2=r^2, where r is the radius; and the same circle in polar coordinates

The equation of can be written as p=r, thus greatly simplifying the equation.

This mathematical knowledge was not difficult for Natalie. She quickly picked up a pen and drew a coordinate system on the paper, marked the numbers on the coordinate system and started drawing.

At the intersection of the two straight lines, an arc is drawn extending to the upper left. The arc draws a small arc downwards, and continues to expand outward after crossing the abscissa line. After reaching the limit, it shrinks inward until it intersects with the abscissa line.

The vertical coordinate lines meet; then draw an arc on the right that first extends to the upper right, crosses the abscissa line, and then continues to expand outwards. After reaching the limit, it shrinks inward until it meets the arc just now and the vertical coordinate line.

are connected at the intersection points.

"Wow!" A beautiful heart shape appeared on the coordinate system, and Natalie exclaimed sincerely, "This equation is so beautiful! It's so romantic that it's beyond imagination!"

"There is also a romantic story here!" Lu Qiujian began to speak in a deep voice, "In 1649, on the streets of Stockholm, 52-year-old Descartes met the 18-year-old Swedish princess Christine.

Several

After the queen, he unexpectedly received a notice that the king hired him to be the little princess's math teacher. He followed the guards who came to notify him to the palace, and he met a girl he met on the street. From then on, he became the little princess's math teacher.

teacher."

"What happened next?" Natalie asked eagerly like an ordinary little girl.

Sure enough, every girl has a princess dream in her heart, even Natalie is not exempt from it. Lu Qiujian continued, "The little princess's mathematics has improved by leaps and bounds under Descartes' careful guidance, and their inseparable relationship every day has made them love each other."

When the princess's father, the king, found out, he became furious and ordered Descartes to be executed. After the little princess Christine begged, the king exiled her back to France, and Princess Christine was also placed under house arrest by her father."

"Descartes fell seriously ill soon after returning to France. He wrote letters to the princess every day. Because the king intercepted them, Christine never received Descartes's letter. Descartes was sending the thirteenth letter to Christine

After that, he died of anger. The content of this thirteenth letter only contained a short formula: r=a(1-private nθ). The king could not understand it and felt that

It turned out that the two of them were not always talking about love. He summoned all the mathematicians in the city to the palace, but no one could solve it. He couldn't bear to see his beloved daughter being depressed all day long, so he handed this letter to

Christine, who has always been depressed." Natalie laughed out of the corner of her eyes when she said this, looking down at the graphics she had just drawn.

"Yes, like you, she immediately drew the graph of the equation. She was very happy when she saw the graph. She knew that her lover still loved her. It turned out that the graph of the equation was in the shape of a heart. This is the origin of the heart-shaped line.

.", Lu Qiujian pointed at the picture and said.

Of course, this story full of close friends cannot stand up to scrutiny. First of all, Christine was 24 years old in 1649 instead of 18; secondly, her father was the famous Gustavus II, who had been married to Lu Cen in 1632.

Unfortunately, he was killed in the battle. By this time, even the bones in the grave were probably rotten. There was no chance of executing Descartes; and Lu Qiujian was the first to see this.

When I wrote the article, the original text was that Kristen drew this pattern on the direct coordinate system, but r=a(1-private nθ) is obviously a polar coordinate equation, and the equation of the heart-shaped line in the rectangular coordinate system should be

It is x^2+y^2+a*x=a*sqrt(x^2+y^2) and x^2+y^2-a*x=a*sqrt(x^2+y^2)

.

There are even more loopholes. However, as a man with normal emotional intelligence, Lu Qiujian knows that romantic feelings are the most important thing for women. As for the truth and logic of the facts, if they are not in line with romance, then go ahead.

Die!

So, if you hear that woman telling you a romantic story about the heart-shaped line, don’t try to point out the flaws in the story, otherwise you will be left alone.

Of course, if your math skills are good enough, you can also draw r=arccos(private nθ) on polar coordinates; x=a*(2*cos(t)-cos(2*t)) on parametric coordinates.

,y=a*(2*privaten(

t)-private n(2*t)), all of these can make a heart-shaped line. Then the image of a romantic academic master will appear in front of the girl, and you will gain the achievements of admiration +5 and favorability +10.

Another crucial step forward on the road to overthrow.

"I think my talent in mathematics may not be as good as Descartes, but I will definitely be happier than him, right?" Lu Qiujian looked at Natalie with gentle eyes and gently held her hand.

Jade hands.
Chapter completed!