The polar coordinate system is a centroid (a=2 in the figure), which is the trajectory formed when a fixed point on a circle rolls around another circle with the same tangent radius, depicting the shape of lovers' hearts, and finally returning to the starting point to form a perfect heart, hence the name.

2、 128√e986

This expression begins with a famous cartoon. A beautiful female student called her sweetheart to the classroom to express her love and wrote 128√e986 on the blackboard (as shown on the left). Then she smiled shyly, and then erased the other parts of the expression as high as e, leaving the English letter I Love you on the blackboard.