Download Classifying Triangles

Classifying
Triangles
Basic Geometry
Notes
Every triangle can be classified 2 ways.
Equilateral Triangle
• 3 Congruent Sides
A
AC = 6 cm
AB = 6 cm
B
BC = 6 cm
C
Scalene Triangle
A
• 3 noncongruent
sides
m CA = 10 cm
m AB = 6 cm
B
m BC = 8 cm
C
Isosceles Triangle
• At least one pair of congruent sides
A
m AB = 6 cm
B
m CA = 6 cm
C
m BC = 7 cm
Right Triangle
A
• 1 right angle
mÐBAC = 52°
mÐABC = 90°
B
• 2 acute angles
mÐACB = 38°
C
Acute Triangle
A
• 3 acute angles
mÐBAC = 70°
mÐCBA = 64°
B
mÐACB = 46°
C
Obtuse Triangle
A
mÐCAB = 102°
mÐACB = 32°
mÐABC = 46°
B
C
• 1 obtuse angle
• 2 acute angles
Equiangular Triangle
• 3 congruent angles
A
• All angles equal 60
degrees
mÐCAB = 60°
mÐABC = 60°
B
mÐACB = 60°
C
Practice Problem #1
For the answer,
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• Classify the triangle 2 ways:
A
m CA = 9 cm
m AB = 4 cm
B
• This triangle is
a Right triangle
AND a Scalene
triangle.
C
m BC = 7 cm
Practice Problem #2
For the answer,
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• Classify the triangle 2 ways:
A
m AC = 6 cm
C
mÐCAB = 109°
m AB = 6 cm
m BC = 10 cm
B
• This triangle
is an Obtuse
triangle
AND an
Isosceles
triangle.
Practice Problem #3
For the answer,
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• Classify the triangle as
specifically as possible:
A
AB = 7 cm
AC = 7 cm
B
BC = 7 cm
C
• This triangle
is Equilateral
AND
Equiangular.
Try These 
Fill in the blanks with either:
A for Always, S for Sometimes, N for Never
1) A triangle ___ has two right angles.
2) A triangle ___ has exactly one acute angle.
3) A triangle ___ has at least two acute angles.
4) An obtuse triangle __ has exactly two acute angles.
5) An isosceles triangle ___ has three congruent sides.
6) An equilateral triangle is ___ isosceles.
The
End
