### Classifying Triangles (4-2)

```Classifying
Triangles
Geometry (Holt 4-2)
K. Santos
Triangle
Triangle—is a figure with 3 sides
A
B
Sides
, ,
Vertices (vertex)
points: A, B and C
C
Triangle Classification—
By Angle Measurements
Acute triangle—3 acute angles
Equiangular triangle—3 congruent acute angles
Right Triangle—one right angle
Obtuse Triangle—one obtuse angle
Classify the triangles-Angles
Classify each triangle by its angle measures
A
B
D
∆BDC
obtuse triangle
∆BDA
Acute triangle
C
Triangle Classification—
By Side Lengths
Equilateral Triangle: 3 congruent sides
Isosceles Triangle: at least 2 congruent sides
Scalene Triangle: no congruent sides
Classify the triangle--sides
Classify each triangle by its side lengths.
12
E
Triangle EHF
isosceles triangle
Triangle EHG
scalene triangle
H
10
11
F
G
Finding side lengths
Find the side lengths of the triangle.
3y – 4
G
GF = GH
3y – 4 = 2y + 3
y–4=3
y=7
GF = 3y – 4
GF = 3(7) – 4
GF = 17
GH = 2y + 3
GH = 2(7) + 3
GH = 17
F
5y - 10
2y + 3
H
FH = 5y – 10
FH = 5(7) -10
FH = 25
```