Teaching objectives:
(1) Guide students to master the area calculation formula and experience its derivation process on the basis of exploration and understanding. Can correctly calculate the area of parallelogram.
(2) Through the observation, comparison and hands-on operation of graphics, develop students' concept of space and infiltrate the idea of transformation and translation.
(3) In mathematics activities, stimulate students' interest in learning, cultivate the spirit of inquiry, and let students feel the close connection between mathematics and life.
Teaching focus:
Understand and master the area calculation formula of parallelogram, and use the formula to solve practical problems.
Teaching difficulties:
Understand the derivation process of parallelogram area formula.
Prepare teaching AIDS and learning tools:
Courseware, rectangular and parallelogram pictures, scissors, parallelogram frame, etc.
Teaching process:
First, create situations and introduce new lessons.
Please look at the big screen (enjoy the picture of Suibin Farm). There are two flower beds at the gate of our school. Xiao Ming thinks the rectangular flower bed is bigger, and Xiao Gang thinks the parallelogram flower bed is bigger. Who is right? Do you want to help them judge? (thinking)
What do you think is the basis for determining the size of flower beds? (Area of flower bed) We will find the area of rectangle, but how to find the area of parallelogram? In this lesson, we will discuss the area of parallelogram together. (blackboard writing topic)
Show the teaching AIDS of rectangles and parallelograms, and guide the students to name the parts of rectangles and parallelograms after observation. What is the difference between a rectangle and a parallelogram? Guide the students to say that all four corners of a rectangle are right angles. Please recall what method we used to find the area when learning the rectangular area formula. Who can tell us? We calculate the areas of rectangles and squares by calculating squares. Then can we also calculate the area of parallelogram by counting squares? (Courseware demonstration)
Second, independent inquiry and cooperative verification.
Explore 1: Explore the area of parallelogram by counting squares.
Please open your treasure chest (schoolbag), which contains two cards scaled down by the teacher from two flower beds. Judge for yourself whether you can find the area of parallelogram by counting squares, and fill in the form carefully according to the prompts. Show me a warm reminder:
① Calculate the number of squares on two graphs, and then fill in the table below. (One square stands for 1㎡, and less than one square is counted as half a square. The teacher emphasized the significance of half a case.
After filling out the form, the students discuss with each other and talk about their findings.
How do you calculate it? Did you find anything? Can you guess what the area formula of parallelogram is? (Student Report)
Question2: Verify the guess by digging and filling.
Xiaoming and Xiaogang's guess after counting the squares is the same as ours, but in order to prove the correctness of their guess, they want to verify it. At the same time, I also want to summarize the area formula of parallelogram. Do you want to attend? Students discuss in groups. Encourage students to try their best to find ways, there are more than one way. )
What patterns did we find? (Default: students will answer to find the area of rectangle and square), and then work in groups: Let's try to find a way to transform parallelogram into the figure we have learned, and then find its area. Please pick up your little scissors and try it! Show the outline of cooperative inquiry: (show the teaching courseware)
(1) Use scissors to transform the parallelogram into other figures we have learned. As few times as possible. )
(2) What patterns can be spelled out after cutting?
Teacher: What graphics did you convert to? Can you talk about the transformation process? What is the relationship between the transformed figure and the parts of the parallelogram? Let's review our discovery process (displayed on the big screen):