CK-12 Geometry-Concepts

http://www.ck12.org Chapter 4. Triangles and Congruence

x+p= 180 ◦

120 ◦+p= 180 ◦

p= 60 ◦

Watch this video for help with the Examples above.

MEDIA

Click image to the left for use the URL below.

URL: http://www.ck12.org/flx/render/embeddedobject/52617

CK-12 Foundation: Chapter4TriangleSumTheoremA

Concept Problem Revisited

The third exterior angle of the triangle below is^6 1.

By the Exterior Angle Sum Theorem:

m^61 + 130 ◦+ 130 ◦= 360 ◦

m^61 = 100 ◦

Vocabulary

Interior anglesare the angles on the inside of a polygon whileexterior anglesare the angles on the outside of a
polygon.Remote interior anglesare the two angles in a triangle that are not adjacent to the indicated exterior angle.
Two angles that make a straight line form alinear pairand thus add up to 180◦. TheTriangle Sum Theoremstates
that the three interior angles of any triangle will always add up to 180◦. TheExterior Angle Sum Theoremstates
that each set of exterior angles of a polygon add up to 360◦.

Guided Practice

1. Findm^6 A.