1. Definition: Two triangles are similar if the ratio of their corresponding three sides is equal. This method is suitable for cases where the lengths of three sides of a triangle are known.
2. Parallel line method: If two parallel lines are cut by a third straight line and the cut corresponding line segments are proportional, then the two triangles are similar. This method is suitable for the situation that some corners or some sides of a triangle are known.
3. Angle equality method: If two angles in two triangles are equal respectively, the two triangles are similar. This method is suitable for the case that some angles of a triangle are known.
4. Comprehensive method: Comprehensive method refers to the method of judging similar triangles by combining the above three methods. Synthesizing all kinds of methods, we can consider all kinds of attributes of triangle more comprehensively, so as to judge similar triangles more accurately.
Similar triangles's learning skills:
1. Understanding the concept: It is necessary to deeply understand the concept and properties of similar triangles, including the definition of similar triangles, equal corresponding angles, proportional corresponding sides, etc. At the same time, we should also understand the relationship between similar triangles and congruent triangles.
2. Mastering judgment methods: There are many judgment methods in similar triangles, which need to be mastered and applied flexibly. Among them, the commonly used judgment methods are: definition method, parallel line method, angle equality method and so on.
3. Familiarity with nature: similar triangles has many properties, which need to be mastered and used skillfully. For example, the corresponding angles of similar triangles are equal, the corresponding sides are proportional, and the similar triangles area ratio is equal to the square of the similarity ratio.
4. Doing the problem: By doing the problem, we can deepen our understanding and mastery of similar triangles's judgment and nature. When doing the problem, we should pay attention to choosing the appropriate judgment method and nature, and pay attention to the relationship between the corresponding edge and the corresponding angle.
5. Summary: After studying similar triangles, we should summarize and summarize in time, and connect the knowledge points in series to form a complete knowledge system. You can summarize the commonly used judgment methods and properties, as well as some common questions and problem-solving methods.
6. Connecting with the practice: similar triangles has many applications in daily life, which can deepen our understanding and mastery of similar triangles. For example, when measuring the height of a building, we can use the properties of similar triangles to calculate the height.