"Isosceles Triangle" PPT Courseware 5

Description

"Isosceles Triangle" PPT Courseware 5

Experimental exploration

Draw an isosceles triangle ABC on the paper, and fold the paper in half so that its two sides AB and AC coincide.

Mark the intersection point of the crease and the bottom edge as D, then unfold the paper and flatten it, and think about the following questions:

Question (1) Is the isosceles triangle ABC an axially symmetrical figure?

Question (2) Are ∠BAC and ∠CAD equal?

Question (3) Are ∠B and ∠C equal?

Question (4) What is the positional relationship between the straight line AD where the crease is located and the bottom edge?

Question (5) Are the lengths of line segment BD and line segment CD equal?

Question (6) Can you summarize the properties of the straight line AD where the crease is located?

Important conclusions

An isosceles triangle is an axially symmetrical figure. The axis of symmetry of an isosceles triangle is the perpendicular bisector of the base.

The vertex bisector of an isosceles triangle, the height on the base, and the midline on the base coincide. It is also called the three lines in one.

The two base angles of an isosceles triangle are equal.

communication and discovery

Draw an equilateral triangle ABC and think about the following questions?

How many axes of symmetry does an equilateral triangle have? Can you draw these axes of symmetry?

Properties of the interior angles of an equilateral triangle

Each interior angle of an equilateral triangle is equal to 60°

Example 1 Try to explain "Each interior angle of an equilateral triangle is equal to 60"

Solution: Because △ABC is an equilateral triangle, AB=AC,

So ∠B=∠C

In the same way ∠A=∠B

So ∠A=∠B=∠C

Because ∠A+∠B+∠C=180°

So ∠A=∠B=∠C=60°

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"Isosceles Triangle" PPT Courseware 6:

"Isosceles Triangle" PPT Courseware 6

The concept of isosceles triangle

A triangle with two equal sides is called an isosceles triangle.

Two equal sides are called waist

The other side is called the bottom side

The angle between the two waists is called the vertex angle

The angle between the waist and the bottom is called the bottom angle...

"Isosceles Triangle" PPT courseware 4:

"Isosceles Triangle" PPT Courseware 4 Course Standard Requirements Explore and prove the property theorem of an isosceles triangle: The two base angles of an isosceles triangle are equal; the altitude line, midline and vertex angle bisector on the base coincide (three lines merge into one). Explore and master the determination theorem of isosceles triangles..

"Isosceles Triangle" PPT courseware 3:

"Isosceles Triangle" PPT Courseware 3 Please tell me 1. What are the properties of an isosceles triangle? 2. How to determine whether a triangle is an isosceles triangle? 3. What are the special properties of an equilateral triangle? An equilateral triangle is an axis-symmetric figure and has three axes of symmetry. An equilateral triangle...

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Update Time: 2024-10-29

This template belongs to Mathematics courseware Qingdao Edition Eighth Grade Mathematics Volume 1 industry PPT template

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