Download Geometry 4-1 Classifying Triangles

Geometry 4-1 Classifying Triangles
A triangle is a three-sided polygon. We name a triangle by
naming the three corners (called vertices
). For example,
a triangle with vertices A, B, and C is named ABC .
We classify triangles in two ways: by their angles
their sides .
and by
An acute
triangle has three acute angles .
A right
triangle has one right angle .
An obtuse
triangle has one obtuse angle .
An equiangular
triangle has three congruent angles
9x - 1
4x + 1
C
5x - 1 = 4x + 1
x=2
AB = 4(2) + 1 = 9
AC = 5(2) - 1 = 9
BC = 9(2) - 1 = 17
3y - 3
5x - 1
A
PAUSE HERE AND TRY THIS ONE.
5 G
3y - 3 = 2y + 5
FG = 2(8) + 5 = 21
+
2y
y=8
GH = 3(8) - 3 = 21
F
HF = 5(8) - 19 = 21
5y 19
H
Use the best description for each triangle.
.
50
68
63
Find the measures of the sides of isosceles triangle ABC.
B
A scalene
triangle has no equal sides .
An isosceles
triangle has at least two equal sides
An equilateral
triangle has three equal sides .
49
acute
isosceles
90
40
right
7
4
9
scalene
.