There is an angle bisector in the problem, which can be perpendicular to both sides.

The perpendicular bisector of a line segment can connect the two ends of a straight line.

The two midpoints of a triangle are connected to form a midline.

A triangle has a midline, and the extended midline is equal in length.

Proportional, completely similar, often parallel lines.

If all the lines are outside the circle, they are tangent to the center of the circle to connect them.

If two circles are inscribed inside and outside, they will be tangent through the tangent point.

When two circles intersect at two points, they are generally called chords.

This is a diameter, this is a semicircle, and I want to make a right angle to connect the lines.

Make an equal angle and add a circle to prove that the problem is not that difficult.

The auxiliary line is a dotted line, so be careful not to change it when drawing.

There is an angular bisector in the picture, which can be perpendicular to both sides.

You can also look at the picture in half, and there will be a relationship after symmetry.

Angle bisector parallel lines, isosceles triangles add up.

Angle bisector plus vertical line, try three lines.

Perpendicular bisector is a line segment that usually connects the two ends of a straight line.

It needs to be proved that the line segment is double-half, and extension and shortening can be tested.

The two midpoints of a triangle are connected to form a midline.

A triangle has a midline and the midline extends.

A parallelogram appears and the center of symmetry bisects the point.

Make a high line in the trapezoid and try to translate a waist.

It is common to move diagonal lines in parallel and form triangles.

The card is almost the same, parallel to the line segment, adding lines, which is a habit.

In the proportional conversion of equal product formula, it is very important to find the line segment.

Direct proof is more difficult, and equivalent substitution is less troublesome.

Make a high line above the hypotenuse, which is larger than the middle term.

Calculation of radius and chord length, the distance from the chord center to the intermediate station.

If there are all lines on the circle, the radius of the center of the tangent point is connected.

Pythagorean theorem is the most convenient for the calculation of tangent length.

To prove that it is tangent, carefully distinguish the radius perpendicular.

Is the diameter, in a semicircle, to connect the chords at right angles.

An arc has a midpoint and a center, and the vertical diameter theorem should be remembered completely.

There are two chords on the corner of the circle, and the diameters of the two ends of the chords are connected.

Find tangent chord, same arc diagonal, etc.

If you want to draw a circumscribed circle, draw a vertical line in the middle on both sides.

Also make a dream circle with inscribed circle and bisector of inner angle.

If you meet an intersecting circle, don't forget to make it into a string.

Two circles tangent inside and outside pass through the common tangent of the tangent point.

If you add a connector, the tangent point must be on the connector.

Adding a circle to the equilateral angle makes it not so difficult to prove the problem.

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.