Circle is a relatively simple geometric figure, and it is a basic geometric figure that must be understood and mastered when learning geometric knowledge. In the past, teachers used to draw circles on the blackboard with compasses, but now they can do it with some professional geometric drawing tools. Let's learn how to draw a circle on the geometric drawing board.

Preparation: Download and install the geometric sketchpad software. Click on Geometry Sketchpad 5.06 to download the free software.

Method one, with the help of a circular tool.

As a very useful mathematical drawing software, the geometric sketchpad can draw a circle in many ways, and the simplest method is to use the circle tool directly. The specific drawing method is as follows: use the mouse to select the "circle tool" in the left column, then click on the drawing board to determine the center of the circle, and then drag the mouse to click at the appropriate position. As for the size of the circle, you can master it yourself.

Draw a circle with the circle tool.

Figure 1: Draw a circle with the circle tool.

Method 2: Draw a circle according to the specified radius.

Drawing a circle is inseparable from specifying the radius of the circle. In addition to drawing a circle directly with the circle tool, you can also draw a circle with a line segment as the radius. The specific operation is as follows: Select the left column line segment tool to draw a line segment AB in the workspace, then select the point tool to draw any point C, select the point C and the line segment AB, and execute the command of "Construct"-"Draw a circle with the center and radius", thus drawing a circle C. ..

Draw a circle according to the specified radius.

Figure 2: Draw a circle according to the specified radius.

Method 3: Establish a polar coordinate system to draw a circle.

Change the coordinate attribute of the function image to polar coordinates, and input sine or cosine analytical expressions to draw a circle. The specific operation is as follows:

Step 1: Establish a polar coordinate system. Click the drawing menu in the menu bar above, and select the grid style-polar grid from the drop-down options, as shown in the figure below, to establish a polar coordinate system.

Polar coordinate system

Figure 3: Establishing polar coordinate system

In addition to polar coordinate system, rectangular coordinate system is the most commonly used, and rectangular coordinate system can also be quickly established in geometric sketchpad. Please refer to: How to draw a plane rectangular coordinate system.

Step 2: Click the "Drawing" menu in the menu bar above, select the "Drawing New Function" command from its drop-down options, enter the sine resolution function in the pop-up drawing function dialog box, and click OK, thus drawing a function image, just like a circle.

Sine function image

Figure 4: Drawing Sine Function Image

Method 4: Construct a circle with three points.

Step 1: Draw three points A, B and C on the geometry sketchpad at will, then select the custom tool in the left toolbar, and then select Circle Tool-Circle Through Three Points in the pop-up tool menu, as shown in the following figure.

Select the circular tool.

Figure 5: Select the circular tool.

Step 2: After selecting the above tools, click points A, B and C in turn with the mouse, thus constructing a circle passing through these three points, as shown in the following figure.

One lap after three o'clock.

Figure 6: A circle with three points is drawn.

The above are four ways to draw a circle with a geometric sketchpad. Each method can draw a circle quickly. Different methods can be chosen for different situations. After learning the above tutorial, you will certainly gain a lot.