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4.1 Notes
Triangles and Angles
Name ________________________
A _____________ is a polygon with three sides. It can be classified by its sides and its angles:
Classification by Sides: (Draw a picture, label, and define each)
Equilateral Triangle
Isosceles Triangle
Scalene Triangle
Classification by Angles: (Draw, label, and define each)
Acute
Triangle
Equiangular
Triangle
Right
Triangle
Obtuse
Triangle
** When you classify a triangle, you must be specific and classify it by its angles and sides**
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Right and Isosceles Triangles
In a right triangle, the sides
that form the right angle are the legs of the right
triangle. The side opposite the right angle is the
hypotenuse of the triangle.
In an isosceles triangle,
the two congruent sides of an isosceles triangle
are the legs and the third side is the base.
Draw and label a picture:
Draw and label a picture:
When the sides of a triangle are extended, other angles are formed: (label the diagrams)
Interior Angles
Triangle Sum Theorem:
Exterior Angle Theorem:
Corollary to the Triangle Sum Theorem:
Exterior Angles