Lesson Triangle Midsegment Public E

There are six basic parts to a triangle

There are six basic parts to a triangle

A
C
B

There are six basic parts to a triangle

A
C
B

three sides

side one

There are six basic parts to a triangle

A
C
B

three sides

side AC
side one

There are six basic parts to a triangle

What is the name of side two?
A
C
B
side two

three sides

side AC
side ?
BC

AB

CA
side three
side one

There are six basic parts to a triangle

What is the name of side three?
A
C
B
side two

three sides

side AC
side BC
side ?
CA
AB
BC

There are six basic parts to a triangle

A
C
B

three sides

three angles
and

There are six basic parts to a triangle

angle one
A
C
B

three sides

three angles
angle A
and

There are six basic parts to a triangle

angle one
angle two
A
Name angle 2
C
B

A

B

C

three sides

three angles
angle A
angle ?
and
angle three

There are six basic parts to a triangle

angle one
angle two
A
Name angle 3
C
B
B
A

three sides

three angles
angle A
angle C
and

angle ?

But there are also more complicated triangle parts
But there are also more complicated triangle parts
A
C
B
But there are also more complicated triangle parts
One of those parts is called...
A
C
B
But there are also more complicated triangle parts
One of those parts is called...
A
...the midsegment.
C
B

To describe the midsegment

A
C
B

To describe the midsegment

A
we must first talk about midpoints
C
B
Let's look at line segment AC
A
C
B
Let's look at line segment AC
AC
A
C
B
Let's look at line segment AC

If we knew the exact middle of line AC

A
C
B
middle point
Let's look at line segment AC

If we knew the exact middle of line AC

A
C
B
Let's look at line segment AC

If we knew the exact middle of line AC

and called that point D
A
C
B
Let's look at line segment AC

If we knew the exact middle of line AC

and called that point D
A
D
C
B
Let's look at line segment AC

If we knew the exact middle of line AC

and called that point D
Point D would be the midpoint of line AC
A
D
C
B
If D is the midpoint of line segment AC then...
A
AB ≅ BC
AD ≅ DC
AC ≅ AB
D
C
B
Now let's look at line segment CB
A
D
C
B
Now let's look at line segment CB
A
D
C
B
CB
Now let's look at line segment CB
If we knew the exact middle point of that line
A
D
C
B
Now let's look at line segment CB
If we knew the exact middle point of that line
A
D
C
B
middle point
Now let's look at line segment CB
If we knew the exact middle point of that line
and called that point E
A
D
C
B
Now let's look at line segment CB
If we knew the exact middle point of that line
and called that point E
A
D
C
E
B
Now let's look at line segment CB
If we knew the exact middle point of that line
and called that point E
point E would be the midpoint of line CB
A
D
C
E
B

Point E is the midpoint of line...

AB
AC
CB
A
D
C
E
B
midpoint of AC
So we have the midpoints of two sides of a triangle.
A
D
C
E
B
midpoint of BC
So we have the midpoints of two sides of a triangle.
If we connect those midpoints with a line...
A
D
C
E
B
So we have the midpoints of two sides of a triangle.
If we connect those midpoints with a line...
A
D
C
E
B
So we have the midpoints of two sides of a triangle.
If we connect those midpoints with a line...
that line is called the midsegment
A
D
C
E
B
The midsegment is any line that connects
So we have the midpoints of two sides of a triangle.
If we connect those midpoints with a line...
that line is called the midsegment
A
two midpoints of the sides of a triangle
D
C
E
B
side AC
?
∡A
?
Identify the parts of the triangle
A
D
side AB
?
C
E
B
∡B
?
midsegment
?
∡C
?
side BC
?
The midsegment has two very special properties:
A
D
C
E
B
The midsegment has two very special properties:
A
D
C
E
B
midsegment DE
The midsegment has two very special properties:
1. it is parallel to the third side
A
D
C
E
B
The midsegment has two very special properties:
1. it is parallel to the third side
A
D
C
E
B
DE and AB
are parallel
The midsegment has two very special properties:
1. it is parallel to the third side
2. and it is half the size of the third side
A
D
C
E
B
The midsegment has two very special properties:
1. it is parallel to the third side
2. and it is half the size of the third side
A
D
C
E
B
DE = ½ AB
Which of the following MUST be true
A
DE⇈AB
CA⇈BA
DE⇈CB
D
C
E
B
A
D
5
C
E
B
A
D
50
C
E
B
A
D
8
C
6
E
B
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