CK-12 Geometry-Concepts

4.1. Triangle Sum Theorem http://www.ck12.org

2. Two interior angles of a triangle measure 50◦and 70◦. What is the third interior angle of the triangle?


3. Find the value ofxand the measure of each angle.

Answers:

1. 72◦+ 65 ◦+m^61 = 180 ◦.

Solve this equation and you find thatm^61 = 43 ◦.

2. 50◦+ 70 ◦+x= 180 ◦.

Solve this equation and you find that the third angle is 60◦.

3. All the angles add up to 180◦.

( 8 x− 1 )◦+( 3 x+ 9 )◦+( 3 x+ 4 )◦= 180 ◦

( 14 x+ 12 )◦= 180 ◦

14 x= 168

x= 12

Substitute in 12 forxto find each angle.

[ 3 ( 12 )+ 9 ]◦= 45 ◦ [ 3 ( 12 )+ 4 ]◦= 40 ◦ [ 8 ( 12 )− 1 ]◦= 95 ◦

Interactive Practice

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