Download Geometry 7th Grade TRIANGLES

Geometry 7th Grade
TRIANGLES
Triangles
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A polygon with three sides
Is the simplest of the polygons
Formed by three straight lines
The interior angles add up to 180 degrees
Exterior angles add up to 360 degrees.
It is a closed figure
Because all angles add to 180 degrees only one
angle can be 90 or more.
• The bisectors of the three interior angles meet in
the center of the triangle.
Triangles Categorized by Sides
Equilateral Triangle
The equilateral triangles has all sides equal and
all angles equal. All angles are 60 degrees
Isosceles Triangle
1. Isosceles triangle has two sides that are
equal the unequal side is referred to as the
base of the triangle.
2. The base angles are always equal to each
other.
Scalene Triangle
• Is a triangle where no sides are the same.
• The angles inside a scalene triangle are all
different degrees as well
• The shortest side is opposite the shortest
angle
• The longest side is opposite the longest angle
The Right Triangle
• In a right triangle there is one and only one
angle that equals 90 degrees
• The side opposite the right angle will always
be the longest side.
• The longest side is called the hypotenuse
• A right triangle can be an isosceles triangle
• A right triangle can NEVER be an equilateral
triangle.
Triangles Categorized by Angles
The Obtuse Triangle
• This triangle has one angle greater than 90
degrees
• The other two angles are less than 90 degrees.
The Acute Triangle
• Has all angles less than 90 degrees.
• All three angles are acute angles.
Equiangular Triangle
• All interior angles are equal
• That means if it is equiangular it is equilateral
Identify the parts of a triangle
• The base of a triangle is where you find the
right angle identified.
• We use the base of a triangle so we can find
the altitude or height of the triangle that is
why we need the right angle.
PARTS OF THE TRIANGLE
THE LONGEST SIDE IS CALLED THE HYPOTENUSE
vertex
A
L
T
I
T
U
D
E
H
E
I
G
H
T
90
degrees
vertex
Base
vertex
AREA OF A TRIANGLE
• TO FIND THE AREA OF A TRIANGLE
• MULTIPLE ONE HALF times THE BASE TIMES
THE HEIGHT (ALTITUDE)
• 1/2bh (memorize this!!!)