TRIANGLES:

Angle Measures,Length of Sides

andClassifying

90o

45o 45o

Classifying Triangles

Classifying Triangles.pptx

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45o 45o

90o

**The sum of the degrees of the interior angles in a triangle is 180.

**To find the missing degrees ~ set up an equation equal to 180 and solve for the variable.

Interior Angles

60o 65o

51o

110o

88o

Calculate the degree of the angles in the triangles below.Calculate the degree of the angles in the triangles below.

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45o 45o

90o

x x

x

x

x

x

1. 2.

3. 4.

xo

34o

Calculate the degree of the angles in the triangles below.Calculate the degree of the angles in the triangles below.

Pull for the answerPull for the answer

35o

xo

51o

x + 6o

2xo

5xo

2x + 7o

12o

Sides of a triangleTry the activity with a partner.  What do you notice?

1. Cut three pieces of straw so that their lengths are 2 inches, 4 inches, and 8 inches. Then lay them flat on a surface and try to form a triangle. Each end of the straw needs to be connected to another end of a straw. Is it possible?

2. You need three pieces of straw that are 4 inches, 5 inches and 7 inches. Then lay them flat on a surface and try to form a triangle. Each end of the straw needs to be connected to another end of a straw. Is it possible?

3. Without actually cutting them out, predict whether these three size straws would form a triangle if put together.

a. 2 in, 3 in, 5 in b. 2 in, 4 in, 5 in

c. 3 in, 4 in, 8 in d. 5 in, 5 in, 8 in

4. What can you say about the three sides of a triangle?

Sides of a triangle

**Triangle inequality rule** Sum of the two smaller sides of a triangle must be larger than the third side.

Ex.  Do the following examples create a triangle?   1.  13cm, 12 cm, 25cm   2.  8ft, 12ft, 7ft   3.  9in, 4in, 4in

Triangle Exterior Angles

* Interior angle ~ inside the figure ~ Angle 1

*Exterior angle ~ outside the figure. It is created by extending the side ~ Angle 2

*Interior and Exterior angle at the same vertex are supplementary. ~ Angle 1 + Angle 2 = 180

2 1

interior angle

Exterior angle

109

13

58x

Example

Sides of a triangle

Perimeter of triangle = add all the sidesPerimeter of triangle = add all the sides

P = 64 yd

26 yd

P = 91 in2x + 1

6x

6x  8

Sides of a triangle

The ratio of the angle measures in a triangle is 1 : 3 : 5.  Find the angle measures.  Then classify the triangle by its angle measures.

Sides of a triangle

The ratio of the angle measures in a triangle is 11 : 14 : 20.  Find the angle measures.  Then classify the triangle by its angle measures.

Sides of a triangle

The ratio of the side lengths in a triangle is 4 : 7 : 9.  The perimeter of the triangle is 120 feet.  Find the length of the sides.  Then classify the triangle by its side lengths.

Sides of a triangle

The ratio of the side lengths in a triangle is 9 : 9 : 11.  The perimeter of the triangle is 116 feet.  Find the length of the sides.  Then classify the triangle by its side lengths.

Triangle Activities

1.  Macs  classzone.com  eworkbook (chapter 10 lesson 1 chapter worksheet)  *counts as classwork grade*

2.  Coloring  classifying triangle trees

3.  Triangle toothpicks  creating and classifying triangles

4.  Worksheet  Even numbers on both sides do in notebooks

1. The ratio of the angle measures in a triangle is 8 : 9 : 19. Find the angle measures. Then classify the triangle by its angle measures.

2. The ratio of the side lengths of a triangle is 4 : 7 : 9. The perimeter of the triangle is 120 feet. Find the side lengths. Then classify the triangle by its side lengths.

3. The first angle is three times the second angle. The third angle is twelve less than twice the second angle. Find the angle measures. Then classify the triangle by its angle measures.

1. classzone.com2. Middle School/Math/NJ/GO3. Find textbook4. Eworkbook5. Chapter 10 Lesson 3

**Counts as a classwork grade**6. Complete Chapter 10 Lesson 27. Complete Chapter 10 Lesson 1 8. Take notebook and rotate around to each picture - answering questions in notebook.

Attachments

classifying triangles.ppt

Classifying Triangles.pptx

Classifying Triangles

Joe Griggs

Subject: Geometry

Grade Level: 7th grade

Two Ways to Classify Triangles

By Their Sides

By Their Angles

Classifying Triangles

By Their Sides

Scalene

Isosceles

Equilateral

Scalene Triangles

No sides are the same length

Isosceles Triangles

At least two sides are the same length

Equilateral Triangles

all sides are the same length

Classifying Triangles

By Their Angles

Acute

Right

Obtuse

Acute Triangles

Acute triangles have three acute angles

Right Triangles

Right triangles have one right angle

Obtuse Triangles

Obtuse triangles have one obtuse angle

Classify this triangle.

Right Scalene

Classify this triangle.

Obtuse Isosceles

Classify this triangle.

Acute Scalene

Classify this triangle.

Acute Isosceles

Classify this triangle.

Obtuse Scalene

Classify this triangle.

Right Isosceles

Triangle Degrees

The sum of the measures of any triangle is 180°.

70°

x

What is the measure of x?

Triangle Degrees

The sum of the measures of any triangle is 180°.

45°

x

What is the measure of x?

Triangle Degrees

The sum of the measures of any triangle is 180°.

What is the measure of x?

x

60°

50°

SMART Notebook

Classifying Triangles

Two Ways to Classify Triangles

By Their Sides

By Their Angles

Classifying Triangles By Their Sides

Scalene Isosceles Equilateral

Scalene Triangles

No sides are the same length

All three angles are different measures

Isosceles Triangles

At least two sides are the same length

Two angle measures are the same

Equilateral Triangles

all sides are the same length

All three angles measure 60°

Classifying Triangles By Their Angles

Acute Right Obtuse

Acute Triangles

Acute triangles have three acute angles

Right Triangles

Right triangles have exactly one right angle

Obtuse Triangles

Obtuse triangles have exactly one obtuse angle

Practice on Your Own

Classify the following triangles by their sides and angles.

Write the response on the whiteboard

1/10/2013

Geometry

11

Classify this triangle.

Right Scalene

Classify this triangle.

Obtuse Isosceles

Classify this triangle.

Acute Scalene

Classify this triangle.

Acute Isosceles

Classify this triangle.

Obtuse Scalene

Classify this triangle.

Right Isosceles

Triangle Degrees

The sum of the measures of any triangle is 180°.

70°

x

What is the measure of x?

Triangle Degrees

The sum of the measures of any triangle is 180°.

45°

x

What is the measure of x?

Triangle Degrees

The sum of the measures of any triangle is 180°.

What is the measure of x?

x

60°

50°

SMART Notebook

Page 1: TitlePage 2: Sum of AnglesPage 3: Calculate - 1Page 4: Calculate - 1Page 5: Calculate - 2Page 6: Dec 13-11:48 AMPage 7: Dec 13-11:48 AMPage 8: Dec 14-11:25 AMPage 9: Feb 21-2:52 PMPage 10: Feb 25-10:18 AMPage 11: Jan 11-9:58 AMPage 12: Dec 13-11:48 AMPage 13: Dec 13-11:48 AMPage 14: Dec 13-11:48 AMPage 15: Dec 13-11:48 AMPage 16: Dec 13-11:48 AMPage 17: Dec 13-11:48 AMPage 18: Jan 14-12:55 PMPage 19: Dec 14-11:38 AMPage 20: Dec 14-11:38 AMPage 21: Feb 25-10:43 AMPage 22: Dec 14-11:39 AMPage 23: Dec 14-11:39 AMPage 24: Feb 20-2:54 PMAttachments Page 1