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The construction of compass and ruler refers to drawing with scale-free ruler and compass. Ruler drawing is a mathematical discipline that originated from ancient Greece.
Only compasses and rulers are used, and only a limited number of times are allowed to solve different plane geometric drawing problems. Ruler The rulers and compasses used for drawing are imaginary, which are not exactly the same as those in reality.
The definition of angle bisector leads a ray from the vertex of an angle and divides the angle into two identical angles. This ray is called the bisector of this angle.
The intersection of bisectors of three angles of a triangle is called the center of the triangle. The distance from the center of a triangle to the three sides is equal, which is the center of the inscribed circle of the triangle. The bisector of an angle of a triangle intersects the opposite side of the angle, and the line segment connecting the vertex of the angle and the opposite side is called the bisector of the triangle (also called the bisector of the inner angle of the triangle).
By definition, the bisector of a triangle is a line segment. Because a triangle has three internal angles, it has three bisectors. The intersection of the bisectors of a triangle must be inside the triangle.
Compass is a tool for drawing circles or strings in mathematics and drawing, and is often used for drawing with a ruler. The invention of the compass can be traced back to the Xia Dynasty in China. "Historical Records Xia Benji" recorded Dayu's "left rope, right gauge" in water control. In Oracle Bone Inscriptions in the 5th century BC/KLOC-there were already rules and moments, which were called "rules" at that time, that is, compasses.
"Zhou Li Kao Gong Ji Craftsman" records: "The craftsman founded the country, the ground hangs, and the raft hangs, depending on the scene. For the rules, know the sunrise scene and the sunrise scene. Participate in the Japanese-Chinese scenery during the day, and the star of the night test is to grab the sky. " Shandong Jiaxiang Wuliang Temple has a brick statue of Fuxi Nuwa in the Eastern Han Dynasty. Nuwa abides by the rules and Fuxi abides by the rules. The rule here is the ancient beam rule.
Its shape is similar to the "Gui" in Oracle Bone Inscriptions. A drawing tool for drawing circles. There are two feet, the upper end is hinged, and the lower end can be separated or closed at will to adjust the radius of the drawn arc.
The end of one foot is a needle tip, and the end of the other foot can be fitted with a foot for drawing pencil lines or ink lines. Some compasses are equipped with telescopic rods to draw larger circles. There are beam compasses, spring compasses and movable core compasses.