"Parallelograms and Their Properties" PPT Courseware 3

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"Parallelograms and Their Properties" PPT Courseware 3

Parallelogram concept: A quadrilateral with two sets of opposite sides that are parallel is called a parallelogram.

Opposite sides: AB and CD, AD and BC

Diagonals: ∠DAB and ∠BCD, ∠ABC and ∠CDA

Diagonal: AC, BD

Mathematical symbol for parallelogram: "□"

Students draw a parallelogram at will, and based on the relevant concepts in parallelograms, through experimental operations and guessing, they try to find and discover as many other characteristics of the parallelogram as possible except that the two opposite sides are parallel.

AB=CD, AD=BC (Conclusion 1)

∠DAB=∠BCD, ∠ABC=∠CDA (Conclusion 2)

∠DAB+∠ABC=∠ABC+∠BCD=∠BCD+∠CDA=∠CDA+∠DAB=180° (Conclusion 3)

Properties of parallelograms:

Property 1. Opposite sides of a parallelogram are equal.

Property 2. The opposite angles of a parallelogram are equal.

Property 3. The diagonals of a parallelogram bisect each other.

Apply what you learn

1. Known: In □ABCD, ∠A=100°, can you find the measures of other angles? Tell me your reasons.

Variation 1. In □ABCD, ∠A is 30° greater than ∠B.

Then ∠A＝＿＿, ∠D＝＿＿.

Variation 2. In □ABCD, if the exterior angle of ∠A is 50°, what is the degree of each interior angle of the parallelogram?

2. As shown in the figure, it is known that in □ABCD, AB=8, BC=4, what are the lengths of the other sides? What is its circumference equal to?

Variation 1. The perimeter of □ABCD is 20. It is known that AB=6, then BC=＿＿, CD=＿＿.

Variation 2. If the perimeter of □ABCD is 30�, AB:CB=3:2, then AD=____�, CD=____�.

Give it a try

How many parallelograms with different shapes can be made from two identical triangle pieces of paper with three unequal sides?

What lessons can be learned from the puzzle?

Summary: A parallelogram can be composed of two congruent triangles. Therefore, when solving parallelogram problems, you can usually connect the diagonals and convert them into two congruent triangles to solve the problem.

Class review

1. Definition: A quadrilateral with two sets of opposite sides that are parallel is called a parallelogram.

2. Properties:

Opposite sides of a parallelogram are parallel and equal.

Opposite angles of a parallelogram are equal.

The adjacent angles of a parallelogram are complementary.

3. Application of properties

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"Parallelograms and Their Properties" PPT courseware 6:

"Parallelogram and Its Properties" PPT courseware 6 1. The concept of parallelogram: 1. Definition: A quadrilateral with two sets of opposite sides that are parallel is called a parallelogram. 2. Characteristics: a. It belongs to a quadrilateral; b. It has two sets of opposite sides. Parallel. 3. Symbol: □ such as parallel four..

"Parallelograms and Their Properties" PPT courseware 5:

"Parallelograms and Their Properties" PPT Courseware 5 Knowledge Review Definition A quadrilateral with two sets of opposite sides that are parallel is a parallelogram. Properties: Opposite sides of a parallelogram are parallel and equal; Opposite angles of a parallelogram are equal; Adjacent angles are complementary. Caught between two parallel lines...

"Parallelograms and Their Properties" PPT courseware 4:

"Parallelogram and Its Properties" PPT Courseware 4 Review: 1. What is a parallelogram? How to express? 2. What are the properties theorems of parallelograms? 3. How to express its property theorem in geometric language? Experiments and Inquiries Please read Chapter 6 of the textbook carefully.

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Update Time: 2024-10-03

This template belongs to Mathematics courseware Qingdao Edition Eighth Grade Mathematics Volume 2 industry PPT template

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