Look at the center line first, and see the center line double. In geometric problems, if the midpoint or midline is given, we can consider crossing the midpoint as the midline or crossing the midline to solve related problems. ?

Secondly, parallel lines are often used in the proof of proportional line segments. When making parallel lines, one ratio in the conclusion is often kept, and then it is linked with another ratio in the conclusion through an intermediate ratio.

Third, for trapezoidal problems, the commonly used methods of adding auxiliary lines are:

1, the two ends of the upper bottom are perpendicular to the lower bottom?

2. Make a waist parallel line at one end of the upper sole?

3. Draw a diagonal parallel line at one end of the upper sole.

4. Make the midpoint of one waist parallel to the other?

5. Does the straight line passing through the endpoint of the upper sole and the midpoint of the waist intersect with the extension line of the lower sole?

6. As the trapezoid center line?

7 extend the waist to make it intersect?

Fourthly, in solving the problem of circle.

1, the intersection of two circles is a chord. ?

2. Two circles are tangent, and the tangent point leads to the common tangent.

3. Look at the diameter at right angles.

4. When encountering tangent problem, is the radius of connecting tangent point a commonly used auxiliary line?

5. When solving problems related to chords, the chord center distance is often made.

The auxiliary line is a dotted line, so be careful not to change it when drawing. If the graph is dispersed, rotate symmetrically to carry out the experiment. Basic drawing is very important and should be mastered skillfully. You should pay more attention to solving problems and often sum up the methods clearly. Don't blindly add lines, the method should be flexible. No matter how difficult it is to choose the analysis and synthesis methods, it will be reduced.

In geometry, it is a part of students' study to make a line or line segment with great value on the basis of the original drawing to help solve geometric problems.

Reveal the hidden nature of graphics: when the logical relationship between conditions and conclusions is unclear, the hidden nature of graphics in conditions can be fully revealed by adding appropriate auxiliary lines. So as to draw a transitional inference and reach a conclusion.