"Understanding Triangles" Triangle PPT Courseware 4

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"Understanding Triangles" Triangle PPT Courseware 4

Observe the roof frame diagram below

Think about it:

1. Can you find four different triangles?

2. Share the triangles you found with your partner.

3. What characteristics do these triangles have in common?

can you answer

1. What characteristics do these triangles have in common?

A triangle has three sides, three interior angles, three vertices, and three line segments connected end to end.

2.What is a triangle?

A figure composed of three line segments that are not on the same straight line and connected end to end is called a triangle.

3. How to represent a triangle?

A triangle can be represented by the symbol "△", as shown in the figure on the right, the triangle is recorded as: △ABC

4. How can the sides of a triangle be represented?

As shown in the figure, the three sides of a triangle can be represented as AB, BC, AC. The side BC opposite to vertex A can also be represented as a, the side AC opposite to vertex B is represented as b, and the side AB opposite to vertex C is represented as c.

If I say that a triangle has three elements, can you guess which three elements they are?

Angles: There are three angles in a triangle: ∠A, ∠B, ∠C.

Vertices: There are three vertices in a triangle, vertex A, vertex B, and vertex C.

Sides: The three sides of a triangle are AB, BC, and AC.

Discuss

(1) On the night of the Lantern Festival, lanterns were lit on the roof beams. Which one is longer, the wire with yellow lanterns or the wire with red lanterns? Give your reasons.

(2) In a triangle, what is the relationship between the sum of any two sides and the length of the third side?

Why? What conclusions can you draw from this?

Practice to improve

1. There are two wooden sticks with lengths of 5cm and 8cm respectively. Can they be arranged into a triangle using a wooden stick with a length of 2cm? Why? What about the wooden stick with a length of 13cm? Move your hands.

Problem solving skills

The value range of the third side of the triangle is: the difference between the two sides < the third side < the sum of the two sides

2. Please use the mathematical knowledge you have learned to explain:

Why do some pedestrians often cross the road instead of using the crosswalk?

Reason: The sum of any two sides of a triangle is greater than the third side. Or the shortest line segment among all the lines between two points.

3. Each of the following numbers is the length of three small wooden sticks. Can they be used to form a triangle? Put it into practice to verify your conclusion.

(1) 3cm, 4cm, 5cm;

(2) 8cm, 7cm, 15cm;

(3) 13cm, 12cm, 20cm;

(4) 5cm, 5cm, 11cm.

What did you gain from studying this class?

1. The concept of triangle

2. The three elements of a triangle

3. Representation method of triangle

4. The relationship between the three sides of a triangle

Keywords: Understanding Triangle Teaching Courseware, Triangle Teaching Courseware, Beijing Normal University Edition 7th Grade Mathematics Volume 2 Courseware, 7th Grade Mathematics Slide Courseware Download, Understanding Triangle PPT Courseware Download, Triangle PPT Courseware Download, .ppt format

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Update Time: 2024-11-22

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