Given the long axis and short axis of an ellipse, which are perpendicular to each other and divided into two, the approximate drawing of the ellipse (four-center approximation method) is as follows:

Step one:

Draw a long axis AB and a short axis CD to connect AC;

Step two:

Intercept CF on AC to make it equal to the difference ce between AO and CO;

Step 3:

The median vertical line is AF, which makes it intersect with AO and OD (or its extension line) at O 1 and O2 respectively. Take O as the symmetry center, and find the symmetry points O3 and O4 of O 1, which are the four centers. Connect lines through O2 and O 1, O2 and O3, O4 and O3 respectively;

Step 4:

Draw two arcs with O2 and O4 as the center and O2C (or O4D) as the radius respectively. Then draw two arcs with O 1 and O3 as the center and O 1A (or O3B) as the radius, so that the contact points of the four arcs are located on the extension lines of O2O 1, O2O3, O4O 1 and O4O3 respectively, and an ellipse is obtained.

Extended data:

Concentric circle method:

It is known that the major axis and minor axis of an ellipse are perpendicular to each other and bisected. The steps of drawing concentric circles of an ellipse are as follows:

Step one:

Make two concentric circles with the center of the ellipse as the center and the lengths of the long axis and the short axis as the diameters respectively;

Step two:

Make an arbitrary straight line passing through the center of the circle, make a big circle at 1 and 2 points, make a small circle at 3 and 4 points, lead the vertical line to pass through 1 and 2 respectively, and lead the horizontal line to pass through 3 and 4, and their intersection points A and B are the points on the ellipse;

Step 3:

Repeat the drawing according to the method in the second step to find a series of points on the ellipse;

Step 4:

Connect these points smoothly with curved plates to obtain the required ellipse.

If the ruler is not drawn correctly, there must be an error.

Unless you draw with CAD.

Command: EL

Painting method 1: stippling at both ends. That is, draw the length of the major axis first, and then enter the value of the minor axis. It's done.

Figure 2: Central stippling. That is, set the center point first, input the long-axis data first, and then input the short-axis data. It's done.

Note: The default drawing method is stippling at both ends. Enter "c" according to the command prompt to perform central stippling.

References:

Ellipse-Baidu Encyclopedia