Understanding of axisymmetric shape

Cutting method of single symmetrical small paper map: take a rectangular paper with a length of 6cm and a width of 5cm and fold it in half, and draw a single small paper map along the crease direction.

Teacher: If I cut along the dotted line, what kind of graphics will appear?

Operation: Cut the dotted line drawn along the crease direction and you will become a complete little paper man.

Student: Look at this little paper man and say, what graphics are we studying? (Axisymmetric figure) Find out where its axis of symmetry is. Ask a student to go to the booth and draw the symmetry axis.

Students cut out a symmetrical paper figure from a small rectangular piece of paper.

Student: Review the cutting method just now, and sum up: fold in half first-draw half a paper figure along the crease line-cut along the dotted line-unfold.

Draw its symmetry axis on the little paper figure you cut.

Error analysis: the booth shows half of the villains who are not related to each other. Q: What is the reason?

(Not along the crease direction, but along the direction of separation after the paper is folded in half, that is, the axis of symmetry is no longer a crease, but one side of the paper).

The cutting method of four small paper men side by side.

The teacher showed it well: four little paper men stood side by side.

Guided observation: what is this number? (Axisymmetric figure)

Student: A single small paper graph is an axisymmetric graph, and the axis of symmetry is in the middle of each small paper graph.

Teacher: The four little paper figures are also axisymmetric figures, and the symmetry axis is between the hands of the second and third little paper figures.

Explore the folding method:

Teacher: Cut a little paper man, and we'll fold the paper in half and divide it equally. (two copies)

Teacher: To cut out four small paper figures side by side, how many parts should we divide the rectangle equally? (8 copies)

Group discussion: How to origami? In which direction? The teacher patrolled the instructions and corrected the incorrect folding.

Teachers and students summarize the folding and drawing methods:

Fold it in half for three times, divide the rectangular paper into eight parts evenly, and draw half a villain along the symmetry axis with the last crease as the symmetry axis. The little paper man's arm should reach to the edge of the paper. Discussion: (Why extend to the edge? What will happen if we don't reach it? )

Cut and spread along the dotted line.

Peer review within the group: Who cut the best works and what experience (the good works recommended by the group are posted on the blackboard).

Guide summary:

Look at the operation chart of the textbook P46.

If you want to cut eight small paper figures arranged side by side and divide them equally, how should you fold them? How to draw? How to cut?

Student: Answer and show the courseware.

Teacher: Show the patterns of four small paper figures cut by yourself in a circle.

Question: A: What's the difference between these little paper men and the little paper men we just cut out? What is the same? Individually, they are all axisymmetric figures, but the difference is that the little paper figures were side by side just now, and now they are in a circle.

B, the little paper man was cut into a rectangle just now. What paper should I use now? (Square paper)

Explore the folding method:

Since a single small paper figure is an axisymmetric figure just now, it means that the final cut we drew is the same as just now, but how can we fold it to make four small paper figures form a circle?

Health: Discussion.

Cut out four small paper figures in a circle. How many parts should the square be divided equally?

Teacher: patrol guidance, correct wrong folding,

Teacher: By folding, can you find the points where four little paper men rotate?

Draw half a villain:

Teacher: We just cut the little paper figures side by side. We drew half a small paper figure along the crease direction (that is, the direction of symmetry axis). Where is the symmetry axis of a single little paper man now? How to draw half a little paper man? Where should the head face? (towards the center)

Teacher: patrol guide.

Cut and spread along the drawing line,

Show the works (the recommended works of each group are posted on the second row of the blackboard)

Guide summary:

Combined with pictures, talk about the cutting method of small paper figures in a circle.

If you want to cut eight small paper figures into a circle, how many parts should you divide the square paper evenly? How to fold it? Courseware display.

Student: Observe the first row of paper-cut works. There is a paper man, how can you move to get the other three paper men? (Translation) Along what translation? (Little paper man's arm)

Student: Observe the paper men in the second row. There is a paper man, how can you move to get the other three paper men? (Rotating) Around what? Show the courseware (the center of the square).

Teacher: What have we learned from cutting these beautiful patterns?

Health: Answer. (Axis movement, translation, rotation)

Student: Using the paper-cutting method just now, design a group of translation paper-cutting works and rotation paper-cutting works in groups, and the patterns are self-determined. (Courseware demonstration requirements)

(Playing music)

Show.