1, connection method: first find the key point, and then connect. For example, the midline, midline, height and diameter of a circle of a triangle.

2. Delay method: This method is often used for questions about the center line. For example, extend a line segment to intersect a known straight line.

3. Make parallel lines through a point outside the line.

4. Draw a vertical line.

5. Make the bisector of the angle.

6. Make the common tangent of two circles.

7. Make an angle equal to the known angle.