First, the teaching design:

1 learning mode:

Congruent triangles's research is actually the first step to study the relationship between two closed figures in plane geometry. This is the simplest and most common relationship between two triangles. It is not only the basis of learning the latter knowledge, but also an important basis to prove that the line segments are equal, the included angle is equal and the two lines are vertical and parallel. Therefore, we must master congruent triangles's judgment method and use it flexibly. In order to make students better grasp this part of the content, we should follow the heuristic teaching principle, create problem scenarios in the form of questions, design a series of practical activities, guide students to operate, observe, explore, communicate, discover and think, make students experience the process of abstracting geometric models from the real world, applying what they have learned and solving practical problems, and really put students in the main position.

2 learning task analysis:

Make full use of the materials and activities provided by textbooks, encourage students to experience activities such as observation, calculation, reasoning and imagination, develop students' concept of space, experience the methods of analyzing and solving problems, and accumulate experience in mathematical activities. Cultivate students' orderly thinking, expression and communication skills, combine intuition with simple reasoning on the basis of intuitive operation, pay attention to the establishment of students' reasoning consciousness and understanding of the reasoning process, and be able to express the reasoning process orderly in their own way, laying the foundation for future proof.

3 students' cognitive starting point analysis:

Through the previous study, students have understood the concept and characteristics of graphic congruence, mastered the relationship between the corresponding edges and corresponding angles of congruent graphics, and made good preparations for exploring the conditions of triangular congruence. In addition, students also have the basic drawing ability of triangles with known conditions, which makes it possible for students to actively participate in the operation and exploration of this lesson.

4 teaching objectives:

(1) Under the guidance of teachers, students actively experience the process of exploring the congruence conditions of triangles and the process of obtaining mathematical conclusions through operation and induction.

(2) Master the judgment methods of triangle congruence, such as edge, angle, angle and angle, understand the stability of triangle, and solve some practical problems with triangle congruence.

(3) Cultivate students' spatial concept, reasoning ability, develop orderly expression ability and accumulate experience in mathematical activities.

5 the focus and difficulty of teaching:

Focus: The exploration process of triangle congruence condition is the focus of this lesson.

From setting the situation to asking questions, and then to hands-on operation, communication and summary, students not only get the conditions of the two triangles, but more importantly, they experience the formation of knowledge, a method of analyzing problems, and accumulate experience in mathematical activities, which helps students better understand and apply mathematics.

Difficulties: The exploration process of triangular congruence conditions, especially after the creation of questions, is difficult for junior one students to conduct a comprehensive and correct analysis and discussion of various situations in the face of open questions.

According to the age, physiological and psychological characteristics of junior one students, they do not have the ability to reason and demonstrate geometric problems independently and systematically, and their thinking is limited and their consideration of problems is not comprehensive. Therefore, we should give full play to the leading role of teachers, prompt and guide them in time, and mobilize the enthusiasm and initiative of all students to participate in cooperative discussions as much as possible, so that students can acquire new knowledge and develop their individual thinking in cooperation and exchanges with others. .

6 teaching process

Teaching Steps Teacher Activities Student Activities Teaching Media (Resources) and Teaching Methods

Audit transition

Introduce new knowledge

Create a scene

raise a question

Build a model

find

Inductive summary

Absorb new knowledge

Integrate applications

And its popularity.

Reflection summary

Refining law

Computer display, guide students to review the definition and nature of congruent triangles.

The computer shows that Xiaoming drew a triangle. How can he draw a triangle that is identical to his triangle? We know that the three sides of congruent triangles are equal and the three angles are equal. So, conversely, six elements are equal, so two triangles must be congruent. However, must the six conditions be met? Can the conditions be as few as possible?

Correct the problems in students' classification and give affirmation and encouragement to the different strategies put forward by students to solve problems, so as to meet the diverse needs of students and develop their individual thinking.

According to the triangle "edge, corner" element classification, teachers and students * * * by induction:

1 One condition: one corner, one side.

Two conditions: two angles; Both parties; One corner and one side

Three conditions: triangle; Trilateral; Two corners on one side; Corners on both sides

Think and do the questions according to the above classification order.

Do, verify.

The teacher collects students' works and compares them.

Compare and draw the conclusion:

When only one or two conditions are given,

There is no guarantee that the triangle will be drawn.

Must be congruent

We will study triangles in three cases.

Determination of congruence.

(1) It is known that the three angles of a triangle are

Draw this 40, 60, 80.

A triangle and compare it with your partner.

suit

Students draw a conclusion and then give examples to understand.

Just a moment, please.

For example: if the teacher uses three in class

The squares and triangles used by students have three angles.

Correspondence is equal to each other, but one is bigger than the other.

Small, obviously unequal; It's like once again

An equilateral triangle with two unequal sides.

Triangles are not equal. Wait a minute.

(2) It is known that three sides of a triangle are

4cm, 5cm, 7cm, draw this triangle.

Form, and compare with peers whether congruence.

Chessboard performance: three sides correspond to two equal parts.

Triangle congruence, abbreviated as "edge"

Edge "or" SSS ".

From the above conclusion, as long as the lengths of the three sides of the triangle are determined, the shape and size of the triangle are determined.