Download Lesson 5-1 - Elgin Local Schools

Lesson 5-1
Classifying Triangles
Ohio Content Standards:
Ohio Content Standards:
Formally define geometric figures.
Ohio Content Standards:
Establish the validity of
conjectures about geometric
objects, their properties and
relationships by counter-example,
inductive and deductive
reasoning, and critiquing
arguments made by others.
Ohio Content Standards:
Make and test conjectures about
characteristics and properties
(e.g., sides, angles, symmetry) of
two-dimensional figures and
three-dimensional objects.
Triangle
Triangle
A figure formed when
three noncollinear points
are connected by
segments.
Acute Triangle
Acute Triangle
A triangle with all acute
angles.
Obtuse Triangle
Obtuse Triangle
A triangle with one obtuse
angle.
Right Triangle
Right Triangle
A triangle with one right
angle.
Scalene Triangle
Scalene Triangle
A triangle with no sides
congruent.
Isosceles Triangle
Isosceles Triangle
A triangle with at least
two sides congruent.
Equilateral Triangle
Equilateral Triangle
A triangle with all sides
congruent.
The angle formed by the
congruent sides is called
the vertex angle.
The angle formed by the
congruent sides is called
the vertex angle.
The side opposite the
vertex angle is called the
base.
The angle formed by the
congruent sides is called
the vertex angle.
base angle
base angle
The side opposite the
vertex angle is called the
base.
The angle formed by the
congruent sides is called
the vertex angle.
The two angles
formed by the base
and one of the
congruent sides
are called base
angles.
base angle
base angle
The side opposite the
vertex angle is called the
base.
The angle formed by the
congruent sides is called
the vertex angle.
leg
base angle
The two angles
formed by the base
and one of the
leg
congruent sides
are called base
angles.
base angle
The side opposite the
vertex angle is called the
base.
The congruent
sides are called
legs.
leg
base angle
The angle formed by the
congruent sides is called
the vertex angle.
The two angles
formed by the base
and one of the
leg
congruent sides
are called base
angles.
base angle
The side opposite the
vertex angle is called the
base.
Classify each triangle by its
angles and by its sides.
Classify each triangle by its
angles and by its sides.
Classify each triangle by its
angles and by its sides.
30°
120°
30°
Find the measures of XY and
YZ of isosceles triangle XYZ if
X is the vertex angle.
X
2n + 2
Y
10
2n - 2
Z
Assignment:
Pgs. 191-192
8-22 evens,
30-36 evens