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Reflection on the Teaching of Grade Seven Mathematics Volume II Intersecting Line

This*** 22-09-08 Reflection on teaching

Introduce the intersection line from the scissors, and guide the students to find the opposite vertex angle and explore its relationship from the intersection line. However, when the concept of vertex angle is introduced from the intersection line, the position relationship described by the students cannot meet the teacher's preset (or textbook definition), and the teacher does not want to be passive at the beginning, so they all behave very "actively", which leads to a bit of misunderstanding in this link.

I want to break through and seek novelty. I hope that the introduction of design can naturally lead to concepts and reveal the connotation. At the beginning, there was a problem that entangled me, that is, the size of the vertex angle is determined by the position relationship, but I asked everyone to draw angles of the same size just after class. Is it logical. After repeated speculation, I finally decided to still design like this. As for the equiangle made by the students on the blackboard, I immediately stressed that equality is the result of observation and imagination, which needs further explanation. After the concept of the top corner comes out, immediately find the life prototype to strengthen understanding and contact life. In identifying whether the given figure is a group of questions about the vertex angle, as expected before the class, the students' geometric language is not skilled and rigorous enough, and I patiently corrected it. The reason is that at the beginning of geometry, students must pay attention to the expression of geometric language and form good habits. In this topic, I always ask students to identify the definitions and strengthen their understanding. In the second question, the problem of how to find corresponding angles in an orderly manner without repetition or omission involves the problem of classification strategies. To prevent digression, it is simply mentioned and not solved in the classroom.

Exploring the property of equal vertex angle is the key and difficult point of this lesson, so my design is to draw and measure the angle first, so that students can have a perceptual understanding, and at the same time, students can realize that measurement is error, so students are asked to record the reading of the angle, and ask whether they can calculate the degree of an angle to the vertex angle according to its degree. In fact, the design of this problem is a link between the preceding and the following. Because it is difficult to prove, the specific degree calculation is used as the foreshadowing. It turns out that this design is conducive to students' thinking, because I heard them say "the same as the calculation" when proving.

Exercises are designed to consolidate students' thinking and transform their thinking. The measurement design of cone top angle is of great interest to students, which is quite challenging. In the presets, the students will have different designs, and the result is the same. They have thought about many designs that have little connection with the knowledge of this lesson, such as measuring the bus length and the diameter of the bottom circle, restoring to draw an isosceles triangle of cross section, and then measuring the top angle. This reflects the flexibility of students' thinking. In order to encourage the thinking of seeking differences and innovation, I recognize and encourage this.

Therefore, the classroom presupposition in this section is sufficient, and the classroom generation is natural. Through this lesson, I realized that the more simple the lesson looks, the more we should carefully study the textbook, and explore its position in the textbook and the mathematical ideas contained in it.

Classroom teaching is always dynamic and dialectical. For the introduction of such an "anti traditional" design, it is harmful to geometry. Do you want to guide students to think of using knowledge of vertex angle in cone vertex angle measurement? Whether a given ruler is a guide or a hint needs to be considered again and again, and a reasonable choice should be made.