"Side of Triangle" PPT

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"Side of Triangle" PPT

Part One: Introduction of New Course

Tell me: What do you know about triangles?

Pages 100-101 of the independent learning textbook: Observation and thinking, what everyone talks about, continue to understand:

1. The concept of triangle

2. Sides, vertices, interior angles of triangles

3. Representation method of triangle

4. Two classification methods of triangles

5. The relationship and application between the three sides of a triangle

Sides of a triangle PPT, part 2: What is a triangle?

1. Definition of triangle

A figure formed by connecting three line segments that are not on the same straight line in sequence is called a triangle.

Therefore, the characteristics of triangles are:

(1) Not on the same straight line (2) Three line segments

(3) Connect head to tail in sequence (forming a closed figure)

2. Representation of triangle:

Triangles are represented by the symbol "△"

Written as "△ ABC" and pronounced as "Triangle ABC"

3. Vertices of triangles

The common endpoints of two adjacent sides of a triangle are called the vertices of the triangle.

As shown in the figure, how many vertices does triangle ABC have? they are, respectively________.

4. Sides of triangle

The three line segments that make up a triangle are called the sides of the triangle.

The three sides of △ABC are sometimes represented by a, b, and c. Generally, the side opposite to vertex A is marked as a, the side opposite to vertex B is marked as b, and the side opposite to vertex C is marked as c.

Sides of Triangle PPT, Part 3: Practice:

1. As shown in the picture, it is a figure composed of three thin sticks. Among them, the figure that conforms to the concept of triangle is ( )

2. How many triangles are there in the picture? Please be smart and use symbols to represent these triangles;

3. As shown in the picture, answer the following questions:

(1). There are ____ triangles in the picture;

(2), ∠1 is the angle of which triangle?

△BDO and △BDC

(3) How many triangles have CE as one side? What are the differences?

Two: △BCE and △COE

Sides of Triangle PPT, Part 4 Content: Question Exploration:

As shown in the triangle in the figure, suppose a bug wants to crawl from point B to point C along the side of the triangle. How many routes can it choose? Are all routes the same length?

Route 1: From point B to point C

Route 2: From point B to point A, and then from point A to point C.

The lengths of the two routes are BC and AB+AC.

From "the shortest line segment between two points" we can get AB+AC>BC

In the same way, we can get: AC+BC>AB,AB+BC>AC

The three sides of a triangle have this relationship:

(1) The sum of two sides of a triangle is greater than the third side

(2) The difference between the two sides of the triangle is less than the third side (why?)

Give it a try:

1. Can the three line segments of the following lengths form a triangle? Why?

(1) 3, 8, 4

(2) 2, 5, 6

(3) 5, 6, 10

(4) 3, 5, 8

think:

To determine whether three line segments can form a triangle, is it necessary to check that the sum of any two of the three line segments is greater than the third? Based on your experience in solving the problem just now, is there an easier way to judge?

Just select two shorter line segments, find the sum and compare it with the longest line segment. If the sum is larger, it is OK; otherwise, a triangle cannot be formed.

Sides of Triangle PPT, Part 5: Analysis of Examples and Exploring New Knowledge

Use an 18cm long string to form an isosceles triangle.

(1) If the waist length is twice the base length, what is the length of each side?

(2) Can it form an isosceles triangle with one side 4cm long? Why?

Expand and apply!

The four oil wells on the grassland are located at locations A, B, C, and D as shown in the figure. Now we need to build a maintenance station H. Where should H be built so that the sum of the distances from it to the four oil wells is HA+HB+HC+HD is the smallest? Give reasons.

1. Where do you think this H should be? Think big!

2. Where is the point with the smallest distance to A and C? To B, D?

Keywords: Free download of Hebei Education Edition mathematics PPT courseware for seventh grade volume 2, PPT download of sides of triangle, .PPT format;

For more information about the "Side of a Triangle" PPT courseware, please click on the "Side of a Triangle ppt" tab.

"Sides of a Triangle" PPT courseware:

The first part of the "Side of a Triangle" PPT courseware content: Triangle analysis Triangle: a figure composed of three line segments that are not on the same straight line connected end to end. Representation of a triangle: Triangle ABC in the picture, recorded as: △ABC, read Make: Triangle ABC ..

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Update Time: 2024-11-15

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