WARM-UP Grab a red pen and have your

homework out ready to grade

ACTIVITY Follow the directions in the handout we

will discuss together

GEOMETRY 4.2: ANGLE

MEASURES OF A TRIANGLE

Objective: ________________________

__________________________________

• Triangle Sum Theorem: The sum of the measures of

the angles of a triangle is 180°.

_______ + _______+ ______= ________

1

2 3

PRACTICE

COROLLARY A corollary to a theorem is a statement

that can be proved easily using the theorem.

Corollary to the Triangle Sum Theorem: The acute angles of a right triangle are complementary.

____ + _____ = ____

PRACTICE

ANGLES OF A TRIANGLE

Interior angle: angle inside the triangle

Exterior angle: angle formed when one side of a triangle is extended

*Only one at each vertex

Exterior Angle Theorem: The measure of an exterior angle of a triangle equals the sum of the measures of the 2 remote interior angles.

_____ + _____ = ______

PRACTICE

ACT PRACTICE

62° 1 2 3

Find the measure of <1, <2, and <3

WARM-UP Grab a ruler from the clear bin on the

counter and partner up with one other person (groups of two)

TODAY Warm-up Objective: TLW define the Sum of angles

in a triangle theorem and apply it along with the corollary to problems

Activity-Sums of angles in a triangle Class practice problems

ACTIVITY

ACTIVITY

ACTIVITY

ACTIVITY Now on your own you and your partner

are to each cut out one more triangle Repeat the steps of the activity and see

if it holds true for triangles that you created on your own

CLASS PRACTICE Grab a blank sheet of notebook paper

PRACTICE

PRACTICE

PRACTICE

PRACTICE

PRACTICE

PRACTICE QUIZ