Compass is a tool for drawing circles or strings in mathematics and painting. It is often made into a pen with two tips, one on the paper and the other on the pencil, and then the pencil is used to draw on the paper. Compasses are made of metal and plastic, including two parts connected by hinges, which can be adjusted.

Compass consists of nib, rotating shaft, compass legs, ruler, hinge, pen body, nib, round core, cursor, groove, marking line, positioning hole, screw, seal and other parts.

The function of two legs of compass is: one leg is a pencil with a thin steel needle in it, which can be mounted on the nib; The other leg is a ruler with a steel needle. This leg can't be mounted on the nib.

At the top of the compass, there is a small piece for people to hold with their fingers, which is convenient for turning and drawing. In addition, there is an extension pole and a chalk line foot. When people want to draw a big circle, but the original two rods are not long enough, they can connect the extension rods. When people want to draw a pink coil, they put on pink thread feet.

Application of compasses;

1. Draw circular figures: The most basic use of compasses is to draw circular figures, such as circles, arcs and ellipses. By adjusting the distance between the two feet, the radius of the drawn circle can be controlled.

2. Measuring circular figures: Using compasses can conveniently measure the radius, diameter and perimeter of circular figures. For example, the radius of a circle can be measured by putting one foot of a compass on the edge of the circle and the other foot on the center of the circle.

3. Divide circular figures equally: Compasses can also be used to divide circular figures equally. For example, put the two feet of a compass on the edge of a circle and make the distance between the two feet equal to the radius of the circle, and then rotate the compass to divide the circle into six equal parts.

4. Drawing curve graphics: By using tools such as compasses (such as rulers), you can draw various curve graphics, such as parabola and hyperbola.

5. Mathematics teaching: Compass is one of the commonly used tools in mathematics teaching, which can help students better understand the nature and application of circle.