Mathematics, compulsory education curriculum standard experimental textbook, the first volume of grade six, 69 ~ 7 1 case, 1 case, 2 cases.
Teaching objectives
1. Through observation, operation, analysis and discussion, students derive the formula of circle area.
2. Simple area can be calculated by formula.
3. Infiltrate and transform ideas, get a preliminary understanding of extreme ideas, and cultivate students' observation ability and hands-on operation ability.
Prepare teaching and learning tools
1.CAI courseware;
2. Divide the circle into 8 equal parts, 16 equal parts and 32 equal parts;
3. Some scissors.
teaching process
First, try to transform and deduce the formula.
1. Determine the strategy of "transformation".
Teacher: Students, think about it. When we can't calculate the area of parallelogram, what method is used to derive the calculation formula of parallelogram area?
Default value:
Guide the students to make it clear that we use the "cut-and-complement method" to transform the parallelogram into a rectangle, and deduce the calculation formula of the parallelogram area.
Teacher: Students, think again. How do we deduce the calculation formula of triangle area?
Teacher: Yes, we "transform" parallelogram and triangle into other figures and derive their area calculation formulas.
2. Try to "transform".
Teacher: So, how can we transform the circle into other figures we have learned? (blackboard title: the area of a circle)
Please look at the screen (demonstrate with courseware), and the teacher will give you a hint first.
Teacher: (The teacher will make an appropriate explanation with the courseware demonstration) If we divide a circle into 16 copies (as shown in Figure 3), then each copy (as shown in Figure 4, where the courseware flashes 1 copy) will be like this. Students, what do you think it looks like?
Teacher: Yes, each one is an approximate triangle. Please think again, what is the relationship between this side of the approximate triangle (directed by the teacher) and the circle?
Default value:
Guide the students to observe and make it clear that both sides of this approximate triangle are actually the radius of a circle.
Teacher: If we recombine these approximate triangles, we can "transform" this circle into other figures. Students, the teacher has prepared an equal circle for each of your groups. Please spell it out and "convert" this circle into other figures we have learned. Let's start!
Default value:
It will be difficult for students to combine figures with this approximate triangle. Teachers should strengthen patrol and targeted guidance, not only to encourage students to spell out their own imaginary graphics, but also to guide students to spell out the simplest and easiest to calculate the area of graphics. In general, students will spell out the following figures (as shown in Figure 5, Figure 6 and Figure 7).