1, knowledge and skills: ① understand the concept and composition of the proposition; 2 will judge the truth value of a given proposition; ③ Initial perception of what is proof.

2. Mathematical thinking: ① Improve students' rational judgment ability by judging the proposition and its truth and falsehood; ② Cultivate students' rigorous mathematical thinking through the study of proof.

3. Problem solving: ① Understand the application of propositions in mathematics, and demonstrate your judgment with proof; (2) lay a good foundation for future study and cultivate application consciousness.

4. Emotional attitude: Through the study of propositions, theorems and proofs, students can learn to judge whether a thing is true or not from a rational perspective, stimulate their curiosity and thirst for knowledge, gain successful experience in solving problems with mathematical knowledge, and establish self-confidence in learning. 3. What are the difficulties and difficulties in teaching?

Teaching emphasis: ① the concept of proposition, distinguishing the setting and conclusion of proposition; (2) judging the truth of the proposition; ③ The process of understanding and proving should be well-founded and gradual.

Teaching difficulties: distinguish the setting and conclusion of a proposition, and the process of understanding and proving. The way to break through difficulties: use daily words to guide and do more exercises to break through. Second, teaching preparation: multimedia courseware, tutoring plan, triangle? Third, the teaching process?

Teaching content and teacher activities?

Student activities? Design intent?

First, create scenarios to introduce topics? In our daily speech, some words judge things, while others just describe things. For example, please tell me which of the following words are used for judgment and which are used for description. ?

(1) Beijing is the capital of People's Republic of China (PRC); ? (2) How clever the students in our class are; ? (3) Waste is shameful; ? (4) Everything revives in spring; ?

What do these statements have to do with mathematics? Shall we study together? (blackboard writing) topic?

Students' sentences to gain perceptual knowledge. From the common in life

Introduce sentences into the topic to stimulate students' interest in learning and desire to explore.

Hope. ?

Second, independent exploration, cooperation and exchange to build new knowledge? Activity 1: observe and discover, understand the proposition? Please read the following sentences:

(1) If both lines are parallel to the third line, then this

Two straight lines are also parallel to each other; ?

(2) Two parallel lines are cut by a third straight line, which complement each other; ? (3) the vertex angles are equal; ?

(4) Add the same number to both sides of the equation, and the result is still an equation.

A statement that judges a thing like this is called a proposition. Activity 2: carefully compare and analyze the structure?

Ask students to observe a set of propositions and think about which parts the proposition consists of. ?

(1) If both lines are parallel to the third line, then these two lines

Straight lines are also parallel to each other; ? (2) Two parallel lines are cut by a third straight line, which complement each other; ? (3) If the sum of the two angles is 90? , then these two angles are complementary; ? (4) Add the same number to both sides of the equation. The result is still the same equation. The proposition consists of two parts: the topic and the conclusion.

The topic is what is known, and the conclusion is what is derived from what is known. Many mathematical propositions can often be written in the form of "if, then". The part connected after "if" is the topic, and the part connected after "then" is the conclusion. Activity 3: Eye-catching, distinguish between true and false?

Which of the following propositions are correct and which are wrong? ? (1) Two straight lines are cut by the third straight line, which are complementary to the inner angle of the side surface; ? (2) Add the same number to both sides of the equation, and the result is still an equation; ? (3) Add two opposite numbers to get 0; ? (4) complementary to the lateral inner angle; ? (5) The vertex angles are equal.

True proposition: if the topic is established, then the conclusion must be established, so

Observe oral answers

Observation conjecture? The concept of inductive proposition. Think independently? What is the structure of inductive proposition in cooperation and exchange? Thinking and feeling? Judge carefully?

Provide students with time and space to participate in mathematics activities and cultivate their ability of observation and induction. Experience observation-induction and other activities, feel the research methods of mathematics, and cultivate students' inductive reasoning ability. It lays a foundation for accurate application of properties in the future.

A proposition is called a true proposition.

Pseudo-proposition: the proposition is established, but the conclusion is not guaranteed. Such a proposition is called a false proposition.

Activity 4: Know the theorem and learn to prove it?

Please judge which of the following propositions is correct. What is a false proposition? ? (1) In the same plane, if a straight line is perpendicular to one of the two parallel lines, it is also perpendicular to the other; ?

(2) If two angles are complementary, they are adjacent complementary angles; ?

(3) What if?

, then a = b；; ? (4) Only one straight line is parallel to a point outside the straight line; ? (5) Two points determine a straight line. Like (1)(4)(5), their correctness is proved by reasoning, and the true propositions thus obtained are called theorems.

The correctness of the proposition needs reasoning to judge. The process of reasoning is called proof.

Is the proposition "In the same plane, if a straight line is perpendicular to one of two parallel lines, it is also perpendicular to the other" true or false? How do you judge? Let's write out this reasoning process and give an example to prove it.

Method extraction:?

Whether a sentence is a proposition depends on whether you can find out the topic and conclusion. To judge whether a proposition is false, just give an example (counterexample), which conforms to the proposition, but does not satisfy the conclusion.

Judge carefully. Cognitive theorem

Think independently?

Just try it.

Hands-on operation Deepen understanding? Refining method

Third, consolidate training?

(1) basic training:

1. Is the following statement a proposition? ? (1) between two points, the line segment is the shortest; ()?

(2) Please draw two parallel straight lines; ? ()? (3) Crossing a straight line other than a straight line