Section 4.7
Medians, Altitudes,
and Perpendicular
Bisectors
WARM UP
Activity Part 1
Draw a triangle.
2) Label it ∆BOY.
3) Measure each side of the
triangle.
4) Find and mark the MIDPOINT
of each side.
1)
Activity Part 2
Draw a line connecting Point B
to the MIDPOINT on the
OPPOSITE SIDE.
2) Draw a line connecting Point O
to the MIDPOINT on the
OPPOSITE SIDE.
3) Draw a line connecting Point Y
to the MIDPOINT on the
OPPOSITE SIDE.
1)
What is a Median?

A segment from a vertex to the midpoint
of the opposite side.
– Always three medians.

See the medians for a given triangle.
B
A
C
What is a Centroid?
Centroid: the point where all three medians
meet
 The medians of a triangle divide one
another into ratios of 2:1.

B
x=6
A
y = 5.5
x y
3
11
C
Activity 2
Draw a triangle.
2) Label it ∆ WIG.
3) Draw a segment from W to the
opposite side so that it makes
a right angle with that side.
1)
What is an Altitude?
The perpendicular segment from a vertex
to the opposite side.
 Altitudes can be drawn OUTSIDE of the
triangle.

B
A
C
Orthocenter:
point where
three altitudes meet
Which line is the
median?
Which line is the
altitude?
a
b
What are Perpendicular Bisectors?
A line or ray that is perpendicular to the
segment at its midpoint.
 Does NOT have to start at a VERTEX

Perpendicular Bisectors

What is true of AB and AC?
A
B
X
C
 Circumcenter:
point where three
perpendicular bisectors meet.
TOGETHER, OPEN YOUR
TEXTBOOK
 Page
 #1-6
155 - Classroom Exercises
Partner Practice
 Page
 TO
I
157 # 19 (a, b, and c)
BE HANDED IN! Make it neat.
only need one per group.