9.1 Angles in Triangles and other Polygons
Types of Angles
Types of Triangles
Triangles can be classified by their angles and their side lengths.
Angles
Side Lengths
What is special about the angles inside an isosceles triangle?
What is special about the angles inside an equilateral triangle?
The sum of the angles in a triangle is _________. These are called
.
are created by extending the sides of the shape.
MFM 1PI – Angles of Triangles and Polygons
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Formula for the Degrees in ANY Polygon
Where n is the number of sides in a polygon,
# of Degrees =
Single Angle in a Regular Polygon (all sides the same length, means all angles are the same)
# of Degrees in ONE angle =
Example 1: There are 10 sides in a decagon.
a) How many degrees inside the decagon?
b) If all the angles are the same, what is each angle?
Supplementary Angle Theorem
Supplementary Angles add to 180o
Complementary Angle Theorem
Complementary Angles add to 90o
Example 2: Write the Supplement of each angle.
a) 95o
b) 27o
c) 138o
Example 3: Write the Complement of each angle.
a) 35o
b) 47o
c) 78o
MFM 1PI – Angles of Triangles and Polygons
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