The area of trapezoid [teaching goal]

1, through the operation activities, experienced the process of deducing the trapezoidal area formula.

2. The area of related graphs can be calculated by using trapezoidal area calculation formula and some practical problems can be solved.

[Teaching Emphasis and Difficulties]

Derive the area formula of trapezoid and use it to calculate.

Derive the area formula of trapezoid by many methods.

[Teaching preparation] Multimedia courseware and two identical trapezoidal papers.

[Teaching process]

ask a question

How to calculate the section of trapezoidal dam?

Second, cooperative exploration.

1, group activities to explore the calculation method of trapezoidal area.

(1) number box.

(2) spelling.

(3) Cutting repair method.

(4) 10% discount.

2. Communication methods

3. Inductive calculation formula

Trapezoidal area = (upper bottom+lower bottom) * height |÷2

S=(a+b)h÷2

Third, practice:

Question 2: By calculating the area of each trapezoid, let the students find that when the base and height of the trapezoid are equal, their areas are also equal.

Question 4: Let the students try it by themselves and then exchange methods.

Re-understanding of Grades [Teaching Objectives]

1, in specific situations, further understand the score, develop students' sense of numbers, and realize the close relationship between mathematics and life.

2. Understand the relationship between the whole and the part by understanding the meaning of the score and combining with the specific situation. Cultivate students' abilities of observation, abstraction, generalization and analogy.

[Teaching Emphasis and Difficulties]

Understand and master the meaning of scores.

Extension of the concept of unit "1"

[Teaching process]

First, take a pencil.

1. On-site organization activities: Please invite two students to take the stage, and each student will take out a box of pencils. As a result, the two students took different amounts. One student took out four and the other took out three.

2. Thinking: Both of them took pencils, but the number of pencils they took out was different. Why? Please think about it and communicate in groups.

3. Give feedback in class. Guide the students to find that the total number of pencils in the two boxes is different, that is, the overall "1" is different.

4, teachers and students * * * Summary: A box of pencils means that a box of pencils is divided into two parts on average, one of which is. However, because the scores are different as a whole, the specific figures are different.

Second, talk about it.

Show the picture in the book:

Combining the actual situation of a book and a cake, I realized that the overall difference of a score is different and the specific figures are different, which further deepened students' understanding of the score.

Third, draw a picture.

One number is □. Please draw this figure. Then organize students to communicate. With the help of intuitive graphics, there is always a □ in a graphic, but the shape of this graphic may be different.

Fourth, practice.

Question 1: Use scores to represent the colored parts in the following picture. Let the students fill it out independently first, and then choose some questions to let the students talk about the thinking process.

Question 2: Please color each score in the picture. Students do it independently.

Question 3: Please draw the following figures separately. Are they the same size?

Question 4: Combine the practical problem of "donating pocket money" and understand the relativity of scores. Ask the students to talk about their ideas and give examples.

Question 5: Infer the length of the whole log according to the actual length of the log; Infer a circle from a circle.

Question 6: Let the students understand the relationship between these scores by filling in the numbers and observing. Let the students fill in the numbers first, and then say what they find.

[Blackboard Design]

Re-understanding of fractions

Take out all your pencils.

I ate three. I ate four.

Why don't you take out as many pencils as possible?

The same score corresponds to the same whole and represents the same specific quantity.

The whole corresponding to the same score is different, and the specific figures are different.