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PPT – Angles Inside the Triangle 4-1A PowerPoint presentation | free to download - id: 6c2b7e-YjVmZ

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Angles Inside the Triangle 4-1A

- What is a triangle?
- What is the sum of the measures of the interior

of any triangle? - How are triangles classified and named?

Definition

- A triangle is a figure formed by three line

segments that connect three noncollinear points.

vertex

C

Side

Side

A

B

Side

vertex

vertex

Naming a triangle

- A triangle is named using its vertices and a ?

symbol. This triangle can be named ? ABC

C

A

B

The Three Angles

- Number the angles of your triangle.
- Cut off each angle of your triangle.
- Arrange your vertices (with the numbers)

together. - What do you notice?

Try It

- Two angles of a triangle measure 40 and 58.

What is the measure of the third angle?

82

?

40

58

Triangle Classification by Sides

E

B

H

A

C

G

I

- Scalene
- no sides congruent.

Equilateral All sides congruent.

D

F

Isosceles two sides congruent.

Special Names for Isosceles Triangles

C

Vertex

Vertex angle

- Leg

Leg

Base

A

B

Base angles

Base Angles

Triangle Classification by Angles

- Acute
- All angles
- are acute.

Right Has one right angle.

Obtuse Has one obtuse angle.

Equiangular All angles are equal.

Special Names for Right Triangles

F

Hypotenuse

Leg

D

E

Leg

Try It Classify each triangle using both angle

and side classification.

Try It

Draw an isosceles triangle, ? PRS, with base PR.

Name the legs and the vertex angle. Draw a right

triangle, ?FGH, with right angle F. Name the

hypotenuse and the legs.

Triangle Angle-Sum Theorem

The sum of the measures of the angles of a

triangle is 180

- What is a triangle?
- A figure formed by three line segments that

connect three noncollinear points. - What is the sum of the measures of the interior

of any triangle? - The sum of the measures of the angles of a

triangle is 180 - How are triangles classified and named?
- Triangles are classified by sides and angles.
- Sides scalene, isosceles and equilateral.
- Angles acute, obtuse, right and equiangular.

Assignment 4-1A

- Page 245, 1-8, 10-14, 25-30