According to legend, the Cartesian formula for the heart line is the content of the 13th letter written by the famous French mathematician Descartes to his lover Princess Christine. There is only this mathematical formula in this letter, and the whole curve of this formula is made, which is the famous heart line!
First, what is the Cartesian heart-shaped line formula
Second, the origin of the Cartesian heart line
In 1650, the 52-year-old Descartes met the 18-year-old Swedish Princess Christine on the streets of Stockholm. At that time, Descartes, who was down and broke, lived a begging life, and all his property was only the tattered clothes he wore and a few math books he carried. Descartes, who was lofty by nature, never asked for charity from passers-by, he just silently bowed his head on the paper to write and draw, concentrating on his mathematical world.
One quiet afternoon, Descartes was sitting in the street, bathed in the sun, working on mathematical problems, when suddenly someone came up to him and tapped him on the shoulder. "What are you doing?" Turning his head, Descartes saw a beautiful young face, a pair of clear eyes like a blue lake, delicate, long eyelashes a wink, she is the little princess of Sweden, the king's favorite daughter Christine.
She crouched down, took Descartes's mathematics book and scratch paper, and began to talk to him. During the conversation, he found that the little girl was quick in thinking and had a keen interest in mathematics.
A few days later, he was unexpectedly informed that the king had hired him to be the mathematics teacher of the little princess, and a puzzled Descartes followed the guards who had come to inform him to the palace, and while waiting in the drawing room, he heard the sound of silver bells in the distance. Turning around, he saw the girl he met in the street a few days ago, and in a panic, he quickly bowed his head.
From then on, he became the princess's math teacher.
The princess's mathematics developed rapidly under Descartes's careful guidance, and they began to become close. Descartes introduced her to his new field of research, the rectangular coordinate system. Through it, algebra and geometry could be combined, and this was the prototype of the analytic geometry later created by Descartes. Led by Descartes, Christine was introduced to the wonderful world of coordinates, and she became fascinated by curves. Being together every day made them fall in love with each other.
In Sweden, a romantic country, a pure and beautiful love quietly sprout.
However, it was not long before word of their love affair reached the king, who was furious and ordered Descartes to be put to death. At Christine's pleas, the king banished him to his country, and the princess was placed under house arrest.
At the time, the continent was in the grip of the Black Death. Descartes, who was in weak health, became seriously ill soon after his return to France. In the countdown to his life, he thought of the princess day and night, and wrote to her every day, looking forward to her reply. However, these letters were intercepted by the king, and the princess never heard from him.
After Descartes sent his thirteenth letter to Christine, he left this world forever. At this time, the little princess who was under house arrest in the palace was still wandering in the corridors of the palace, missing her lover in the distance.
This last letter contained no sentence, just an equation: r=a(1-sinθ).
The king could not understand this equation, thinking that there were hidden secrets of two people, and summoned all the mathematicians in the city to the palace, but no one could solve the function. He could not bear to see his beloved daughter unhappy every day, so he gave her the letter. Christine was ecstatic when she got the letter, she immediately understood the lover's intention, got a pen and paper, and began to draw the equation graph, a heart pattern appeared in front of her eyes, Christine could not help but shed tears, this curve is the famous "heart line".
After the death of the king, Christine inherited the throne, after ascending the throne, she immediately sent someone to France to find the whereabouts of her sweetheart, but received the news that Descartes died, leaving a permanent regret...
This world-renowned alternative love letter is still preserved in the European Cartesian Memorial, commemorating this beautiful love.