1. Triangle Application Theorems
Lesson 7.1

2. Theorem 50- The sum of the measures of the angles of a triangle is 180º.

3. Exterior angles of a polygon
Definition- an exterior angle of a polygon is an angle that is adjacent to and supplementary to an interior angle of the polygon.

4. More Theorems!
Theorem 51- The measure of an exterior angle of a triangle is equal to the sum of the measures of the remote interior angles.
Theorem 52- A segment joining the midpoints of two sides of a triangle is parallel to the third side and its length is 1/2 the length of the third side. (Midline Theorem)

5. Proof of Theorem 51- m<BCA +m<1 = 180
m<BCA + m <B + m<A = 180
m <BCA + m <1 =m <BCA + m <B +m <A
m <1 = m <B + m <A