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​Elliptical compass

The reciprocating motion consisting of two axes is converted into a circular motion, and the end used as a handle is a mechanism that draws an ellipse. The manual ellipse compass was devised to literally draw an ellipse. It seems that it was used in architectural design scenes and when drawing patches and emblems, but nowadays, personal computers (CAD, etc.) have become the mainstream. There is also a description that Leonardo da Vinci also used it when drawing. (Reference: Tokyo National Museum Special Exhibition "Leonardo da Vinci-Real Image of Genius" March 20th (Tuesday) -June 17th (Sunday), 2007)

  Exhibits below: Free department store dictionary "Wikipedia"

An ellipse is a curve created from a set of points such that the sum of the distances from two fixed points on a plane is constant. The two reference fixed points are called the focal point. The closer the two focal points are, the closer the ellipse is to a circle, and when the two focal points match, the ellipse becomes a circle centered on that point. Therefore, the circle can be considered as a special case of an ellipse. When a straight line passing through two focal points is drawn inside an ellipse, this is called the long axis. The length of the major axis is called the major axis. At the intersection of the major axis and the ellipse, the difference in distance from the two focal points is maximum. When a vertical bisector of the long axis is drawn inside an ellipse, this line segment is called the short axis. The length of the minor axis is called the minor axis. In Chinese, the elliptical ellipse is thought to have been named after the shape of a "tree stump," meaning "tree stump." In Japan, it was called "Ohitsu" or "flat oval" because of the actual shape of the field, but Seki Takakazu called it "side circle". In the Edo period, many were called side circles and became called ellipses in the Meiji era.


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