Lesson- Isosceles Triangles E
Isosceles triangles have
Isosceles triangles have
two sides equal.
Isosceles triangles have
two sides equal.
triangle
Isosceles triangles have
two sides equal.
two equal sides
B
Which triangle looks like an isosceles triangle?
C
A
∆ABC
∆EFD
∆XYZ
F
D
E
Z
X
Y
5
In an isosceles triangle
In an isosceles triangle
isosceles
triangle
In an isosceles triangle
the base angles
In an isosceles triangle
base angles
the base angles
In an isosceles triangle
the base angles are equal.
In an isosceles triangle
the base angles are equal.
In an isosceles triangle
the base angles are equal.
In an isosceles triangle
the base angles are equal.
equal angles
B
C
A
Which angles are base angles?
∡A and ∡C
∡B and ∡A
∡B and ∡C
Base angles are 
equal
not equal
An easy way to determine which angles
An easy way to determine which angles
are the base angles:
An easy way to determine which angles
highlight where the equal sides meet
are the base angles:
An easy way to determine which angles
highlight where the equal sides meet
are the base angles:
isosceles
triangle
An easy way to determine which angles
highlight where the equal sides meet
are the base angles:
equal sides
An easy way to determine which angles
highlight where the equal sides meet
are the base angles:
An easy way to determine which angles
highlight where the equal sides meet
are the base angles:
An easy way to determine which angles
highlight where the equal sides meet
are the base angles:
equal sides meet here
An easy way to determine which angles
highlight where the equal sides meet
are the base angles:
This is the 'roof' of
the triangle
An easy way to determine which angles
highlight where the equal sides meet
roof
are the base angles:
This is the 'roof' of
the triangle
An easy way to determine which angles
highlight where the equal sides meet
are the base angles:
This is the 'roof' of
and the base angles 
the triangle
are at the bottom
An easy way to determine which angles
highlight where the equal sides meet
are the base angles:
angles
base
This is the 'roof' of
and the base angles 
the triangle
are at the bottom
Identify the 'roof'
A
C
B
X
Z
Y
Q
N
M
R
P
L
Roof
?
Base
?
An equilateral triangles has all the sides equal
An equilateral triangles has all the sides equal
Equilateral Triangle
An equilateral triangles has all the sides equal
An equilateral triangles has all the sides equal
An equilateral triangles has all the sides equal
8
Since all the sides are equal
Since all the sides are equal
equal sides
Since all the sides are equal
then the angles must be equal as well
Since all the sides are equal
then the angles must be equal as well
Since all the sides are equal
then the angles must be equal as well
Since all the sides are equal
then the angles must be equal as well
Since all the sides are equal
then the angles must be equal as well
Equal Angles
That means each angle must be 60 in an 
Since all the sides are equal
then the angles must be equal as well
equilateral triangle
Each angle in an equilateral triangle is
参加了这次测试的学生也参加了 :

创建 That Quiz — 为数学和其它学科出题和测试的网站.