7-2: exterior angle theorem. e xterior a ngle : an angle of a triangle that forms a linear pair with...
TRANSCRIPT
7-2: Exterior Angle Theorem
7-2: Exterior Angle Theorem
EXTERIOR ANGLE: An angle of a triangle that forms a linear pair with one of the angles of the triangle.
REMOTE INTERIOR ANGLES: The angles that do not form a linear pair with the exterior angle.
Exterior AngleRemoteInteriorAngle
7-2: Exterior Angle Theorem
Identify each exterior angle.Then, identify the remote interior angles
Note that each exterior angle at a vertex share the same interior angles
Exterior Angle Remote Interior Angles
4 2 & 3
5 1 & 3
6 1 & 3
7 1 & 2
8 1 & 2
9 2 & 3
7-2: Exterior Angle Theorem
Theorem 7-3 (EXTERIOR ANGLE THEOREM): The measure of an exterior angle of a triangle is equal to the sum of its two remote interior angles. 4 = 1 + 2
Discuss Proof 41
2
3
7-2: Exterior Angle Theorem
If m2 = 38 and m4 = 134, what is m5? 4 = 2 + 5 134 = 38 + 5 96 = 5
If m2 = x + 17, m3 = 2x, and m6 = 101, find the value of x. 6 = 2 + 3 101 = x + 17 + 2x 101 = 3x + 17 84 = 3x 28 = x
7-2: Exterior Angle Theorem
Your Turn What is 1 if m3 = 46 and m5 = 96?
142 If m2 = 3x, m3 = x + 34, and m6 = 98, find the
value of x. Then, find m3. x = 16 m3 = 50
7-2: Exterior Angle Theorem
Two “common sense” theorems are derived from the Exterior Angle Theorem. Theorem 7-4: The measure of an exterior angle of a
triangle is greater than the measure of either of its two remote interior angles.
Theorem 7-5: If a triangle has one right angle, then the other two angles must be acute.
7-2: Exterior Angle Theorem
Assignment Worksheet #7-2