Types of Triangle and Angles of

TrianglesClassification and

Properties

Types of Triangles• Classification by Angles:

______________- the largest angle in the triangle is 90

______________- the largest angle in the triangle is less than 90

______________- the largest angle in the triangle is greater than 90 ______________- All three angles are congruent

Types of Triangles

•Classification by Sides:_______________: No sides have

equal measure _______________: At least two sides have equal measure _______________: All three sides have equal measure

Group Poster Activity:• Each member of your group should take one or

two cards colored triangle cards and measure any missing angles and any missing sides with your protractor or ruler on your formula chart.

• Classify each triangle by sides and ALSO by angles, and paste on a poster like the demonstration on the white board

• Any section on your poster that does not have a picture, you and your group members should discuss if the picture can be drawn.

• If so, draw it on the poster, if not, write • “IS NOT POSSIBLE” in that section of your

poster. • 15 minutes for this activity, and then • you will have to divide responsibilities for

homework so poster is completed by next class

Special Triangle Theorems Related to

ANGLES!!!• ___________________________: The sum of the measures of ALL the angles in a triangle is 180

• ___________________________: The measure of ONE exterior angle of a triangle will be equal to the sum of the measures of the two non-adjacent interior angles, These angles are sometimes called remote interior angles.

• ___________________________: When two angles of a triangle are congruent then the sides opposite thoseangles are congruent, THE CONVERSE IS

ALSO TRUE!

DEMONSTRATION:Sum of Interior

Angles of a Triangle Theorem

Remote Interior Angle Theorem Example:

80

60 140x

Isosceles Triangle Theorem Example:

54

x

Homework Examples:

(6y 20)° (8y + 6)°

8y°

Homework Examples

(5x 8)°

(4x + 20)°

HOMEWORK EXAMPLES:

y° (4y 22)°

60°

Homework Examples:

132°

(3x + 2)°

(2x 7)°