Adding the center line, in an isosceles triangle, you can usually get a lot by adding one, such as adding the center line and bisecting the angle. This is the most commonly used, you can choose to add it according to the formula, but after adding it, you should know what conclusion you can draw, and generally you should find out the congruent triangles, and it is easier to find the congruence condition according to this. When we encounter difficulties, we can tear down the simple graphics and find the basic graphics we have done before, but. It is a good idea to find out the basic graphics, and add auxiliary lines as needed. Don't be blind, otherwise the more you think about it, the harder it will be. If you have a corner and divide it in two, you must want to be vertical. In isosceles, it is very difficult to combine three lines into one, and the difficulty lies in the auxiliary line. Auxiliary line, how to add it? Master theorems and concepts. We must study hard and find out the rules by experience. 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. Study with an open mind and practice hard, and your grades will rise linearly. If you understand, you will understand, so that you will have a bottom in your heart and you will not be afraid to take the exam again. After reading thousands of books, you will write a paper called J. After handing out the test paper, it is most important to take 3 minutes to examine the amount of questions and then grasp the time allocation. The exam is not for you to solve difficult problems, but for you to get high marks. As for the auxiliary line, the question is generally "there is no way to answer doubts, and it is very important to supplement." It is important to pay attention to practice and summary after practice, not just to go. I hope the teacher's answer can enlighten you. I wish you success and bright future. J auxiliary line depends on the situation. It's best to do it on a triangle line, and it's best to add a vertical line between lines. If it is a messy quadrilateral line, it is best to have auxiliary lines to make it a good quadrilateral line, and translation is the best. I don't seem to have many questions to add J 1 and the bisector of the auxiliary line in the senior high school entrance examination: because the bisector is an axisymmetric figure, there are basically the following two kinds (. When you see the middle vertical line, immediately talk about the two ends of the line segment and complete it into an isosceles triangle. Usually, the appearance of the middle also means the midpoint 3. The midpoint should be considered as (1) the hypotenuse median line 4 of the right triangle is in the hypotenuse half (2) median line (3). Midline: double length midline