Transcript 7.1 Triangle Application Theorems

Bellwork
(Turn in on ½ sheet!)
• If DB is a median, is it also an
altitude?
7.1
Triangle
Application
Theorems
Students will be able to:
Apply the Angle Sum, Exterior
Angle and Midline Theorems.
Angle Sum Theorem
• The sum of the interior angles of a
triangle is __________!
Ponder?!?
• Find the m<1.
Exterior Angle Theorem
(Toolbox!)
• An exterior angle of a triangle is
equal to the sum of the two remote
interior angles of a triangle.
Example 1
• In triangle ABC, the sum of m<A and
m<B = 100, the sum of m<B and
m<C = 140. Find the measure of
<A.
Example 2
• If one of the angles of a triangle is
80 degrees, find the measure of the
angle formed by the bisectors of the
other two angles.
Example 3
• If one of the angles of a triangle is
40 degrees, find the measure of the
angle formed by the bisectors of the
other two angles.
Midline (Defn)
• The segment connecting the midpoint of two
sides of a triangle.
Midline Theorem (Toolbox!)
• The midline of a triangle is parallel to
and ½ the length of the third side.
Example 4
• Given: EFGH is a rectangle.
FH = 20; J, K, M, and O are midpoints.
a. Find the perimeter of JKMO.
b. What is the most descriptive name
for JKMO?
Ticket to Leave
• Take out a ½ sheet paper.
• Do Pg. 299 #4.
• When you are finished, turn it on the
desk up front.
Homework
• Pg. 298 # 1-3, 5-12 all, 15, 18
Example 2
• Find the measures of the numbered
angles.