Triangle Theorems and Special Angle Relationships

Properties of Triangles

Lesson 13 - 1: Angle Relationships in Triangles

Lesson 13 - 1 Angle Relationships in Triangles

• Learning Targets:

• Prove theorems about angle measures in triangles

• Apply theorems about angle measures in triangles

Triangle Sum Theorem

• Given the triangle at the right,

• Cut the three angles from the triangle

• Line the angles beside each other on the next slide

Triangle Sum Theorem

• The three angles will form a line

• The sum of the angles equal

   $180\degree$  

•  $43\degree\ +\ 32\degree\ +105\degree\ =\ 180\degree$  

 Find the measure of   $\angle A$   

•  $m\angle A=180\degree-\left(30\degree+96\degree\right)$  

•  $m\angle A=180\degree-126\degree$  

•  $m\angle A=54\degree$  

Multiple Choice

What is the measure of  $$\angle B$$   ?

• $$m\angle B=75\degree$$  

• $$m\angle B=115\degree$$  

• $$m\angle B=105\degree$$  

• $$m\angle B=95\degree$$