5.1 Midsegment Theorem
and Coordinate Proof
LEARNING TARGET: STUDENTS
WILL BE ABLE TO USE
PROPERTIES OF MIDSEGMENTS
AND WRITE COORDINATE
PROOFS.
FEBRUARY 12, 2014
Ex 1: Use the Midsegment Theorem to Find Lengths
 Theorem 5.1 Midsegment Theorem
A midsegment connecting two sides
of a triangle is parallel to the third side
and is half as long.
Find the value of x.
Here, P is the midpoint of AB, and Q is the
midpoint of BC. So,
is a midsegment.
Ex 2: Use the Midsegment Theorem
If AC = 3y – 5 and HJ = 4y + 2, what is HB?
H
HJ = 2AC
AC = HB
4y + 2 = 2(3y – 5) HB = 3(6) – 5
A
B
HB = 13
4y + 2 = 6y – 10
G
C
J
12 = 2y
6=y
Guided Practice
1) DE is the midsegment of ΔABC. Find the value of x.
B
D
22
x
C
E
A
Assignment
Pg. 298 #1, 4, 6-11, 24, 26