The teaching content of this lesson is "Intersection and Parallelism" on page 39-4 1 of "Mathematics for Primary Schools in Grade Four and Six in Nine-Year Compulsory Education". This lesson is based on students' understanding of concepts such as line segment, ray, straight line and angle. In teaching, students can fully perceive the parallel intersection of two straight lines on the plane in specific life situations. There are many similarities in life, which are the realistic background and meaningful materials of this unit. Teaching materials combined with life situations to teach the positional relationship between two straight lines has three advantages: first, it helps students to form mathematical concepts by virtue of life experience; Second, it helps students to understand the close relationship between mathematics and life; Third, it is helpful for students to observe from a mathematical point of view.

Analysis of learning situation

Based on the concept, we must reform the situation that teachers always "talk" and students passively "listen" in classroom teaching, fully trust students, give them the initiative to learn, and fully mobilize their enthusiasm for learning. Therefore, I have constructed a vertical structure of inquiry learning in primary school mathematics classroom teaching, that is, the basic teaching mode of "doubt passion-guide inquiry-application improvement-exchange evaluation".

Teaching objectives

1. Make students understand the parallel and intersecting (including vertical) relationship between two straight lines on the plane, know the parallel lines and vertical lines, and know the distance from the point to the straight line.

2. Through operation and cooperation, students can draw parallel lines and vertical lines with tools such as straightedge, trigonometric ruler and protractor, and can determine the distance from the measuring point to the straight line.

3. Make students experience activities such as perception and observation, operation and drawing in practice, deeply feel the positional relationship between straight lines and develop the concept of space.

4. Let students feel the parallel and vertical phenomena in life and understand the application of equality and vertical in real life; Can actively participate in observation, operation and other learning activities, interested in graphics, feel the fun of mathematics learning.

Teaching emphases and difficulties

Teaching emphasis: Combining with life situation, let students feel the parallel relationship between two straight lines on the plane and know the parallel lines.

Teaching difficulty: 1, can identify which straight lines or line segments are parallel to each other.

2, can draw parallel lines with the help of straightedge, triangular ruler and other tools.

teaching process

First, understand "in the same plane"

Teacher: The teacher also brought an old friend of yours today. This is a cuboid that we met in the second grade.

Show me two rectangular boxes. )

Teacher: Is there a yellow line and a blue line on the top of the box on the same plane?

Teacher: Come and feel it, (now)

Teacher: move a box and ask, are the two straight lines still on the same plane? (not in)

Teacher: Today, let's study the relationship between two straight lines in the same plane.

(blackboard writing: two straight lines on the same plane)

Second, understanding parallelism.

1.

Teacher: "Please come and observe the teacher. There are three groups of straight lines here. " (Computer display)

"Observe how many straight lines there are in each group?" "And these two straight lines are there? (in the same plane) "

2. Classification comparison, parallel understanding

(1) Teacher: "Can you classify these three groups of straight lines according to their positional relationship in each group of pictures? Tell me in the group how you divide it? "

Students communicate and report in groups.

Students may appear:

Some of the two straight lines are connected and some are separated. When students talk about connection or intersection, the teacher explains: In our mathematics, we call two straight lines intersection. (blackboard writing)

B yes, there is. Two straight lines are placed horizontally and vertically, and some are placed obliquely.

Don't deny the students' answers yet, focus on the third group. Teacher: "We all know that straight lines can extend indefinitely. Please close your eyes and imagine what would happen if these two straight lines were extended indefinitely. Computer demonstration (also intersecting)

Refers to the second group Q: What about this group? (disjoint) computer demonstration

Teacher: "So which two components should we put in the same category?" Computer demonstration

(3) Summarize the concept: "In the same plane, two straight lines may or may not intersect. (Writing on the blackboard while talking) Then two straight lines that do not intersect in the same plane are called parallel to each other, and one of them is parallel to the other. " Students read it twice.

Further deepening: "If one of these two straight lines is represented by straight line A and the other is represented by straight line B, we can say that straight line A and straight line B are parallel to each other, and straight line A is parallel to straight line B, what else can we say? (Line B is parallel to Line A ...) The computer shows two straight lines.

(4) Teacher: "Can you use two index fingers to represent two straight lines to represent intersection and parallelism?" Students make gestures. The teacher makes another gesture that is not in the same plane to judge and tell why they are not parallel.

(5) Give examples in life

Teacher: "We met parallel lines just now. In fact, there are many parallel lines in our life, such as blackboard, swing frame and staff. Students, where else have you seen two parallel line segments? (Students give appropriate examples) "

(6) Do the "Want to Do" question 1

Teacher: "It seems that the students have a preliminary understanding of parallelism. The teacher will test you. Can you find out which groups of straight lines in the picture are parallel to each other? " Students raise their hands to answer, ask the reason when it comes to non-parallelism, and read back the concept.

Transition: Are there parallel lines in the figure we know?

(7) Do the third question "Think about it and do it"

"Which line segments in the following figures are parallel to each other? How many groups of parallel lines are there? "

Third, learn to draw parallel lines.

1, explore drawing parallel lines.

(1) Question: "After seeing so many parallel lines, do you want to create a set of parallel lines in your own way? Ok, next, students can draw a picture with the materials given to you by the teacher, fold it with paper, or put it on with a pen. "

(2) Report the creative process.

Teachers choose several kinds in the tour, such as using bitmap, grid paper,

Pay special attention to folding with colored paper. If so, how to fold it, because it is wrong to fold it casually. (The teacher demonstrates it again). Each student makes a discount according to the way the teacher handed it to you. Measure the length of each crease and see what you find. (Each crease is equal in length)

2. Teach to draw parallel lines.

Teacher: "The students are so clever that they have come up with so many methods, but what should we do if we draw a set of parallel lines with specified spacing in the notebook, which can't be folded and there is no sketch?" Let's see how reading teaches us to draw parallel lines.

A computer demonstration painting. (video)

Refining method: one drawing (line), two leaning (ruler), three translating (triangular ruler) and four drawing (line). (The teacher writes on the blackboard at the same time)

B "See it clearly? Ok, let's talk about the process of drawing parallel lines together, and the teacher will demonstrate it slightly obliquely on the blackboard.

Students try to draw by themselves. The teacher went down to instruct and reminded the two rulers not to move.

Fourth, consolidate and improve.

1, draw parallel lines of known straight lines.

Teacher: "What would you think if the teacher gave you a straight line and asked you to draw a parallel line with a known straight line?" ? Is it different from the four steps of randomly drawing a set of parallel lines? (To draw a parallel line of a known straight line, you can overlap one right-angle side of the triangular ruler with the known straight line, translate the triangular ruler with a ruler, and then draw a straight line along the other right-angle side of the triangular ruler. In this way, two straight lines are parallel. Students practice the teacher's patrol on the study list.

2. "What do you think you can do if you want to have a known stippling? What is the key? " (You need to translate the other side of the triangular ruler to a known point before drawing. ) Students try to draw.

3. Think about doing five questions: Which figure is translated by several squares in which direction? How many line segments are there in the picture before translation? What about the translated graphics? Can you find several groups of parallel line segments in the pre-translation picture and the post-translation picture? Roll call

Summary: Translate the graph, and all the corresponding line segments in the graph before and after translation are parallel and equal.

Verb (abbreviation for verb) class summary:

"In this class, we met parallel lines (blackboard writing topic) together. What have you learned from this course? "

Summary: "In fact, parallelism is everywhere in our lives, not only because of its beauty, but also because of its important significance. Why do many things have to be arranged in parallel or made in parallel? After class, we can check the information, continue to study and write an article about parallel math diary. "