CK-12 Geometry - Second Edition

4.1. Triangle Sums http://www.ck12.org

14.

15.

16. Find the lettered angles,a−f, in the picture to the right. Note that the two lines are parallel.


17. Fill in the blanks in the proof below.Given: The triangle to the right with interior angles and exterior angles.
    Prove:m^64 +m^65 +m^66 = 360 ◦

Only use the blue set of exterior angles for this proof.

TABLE4.3:

Statement Reason

1. Triangle with interior and exterior angles. Given
   2.m^61 +m^62 +m^63 = 180 ◦
   3.^6 3 and^6 4 are a linear pair,^6 2 and^6 5 are a linear
   pair, and^6 1 and^6 6 are a linear pair


2. Linear Pair Postulate (do all 3)
   5.m^61 +m^66 = 180 ◦
   m^62 +m^65 = 180 ◦
   m^63 +m^64 = 180 ◦
   6.m^61 +m^66 +m^62 +m^65 +m^63 +m^64 = 540 ◦

194 7.m^64 +m^65 +m^66 =^360 ◦