Types of Triangles 3'6

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Types of Triangles 3.6
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Definition

• A triangle is the union of three line segments
  that are determined by three non collinear points.

Vertex A, B , C Point D is the interior of the
triangle. Point E is in the exterior of the
triangle.
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Triangle Classifications

• Triangles may be classified by either congruent
  sides or congruent angles.

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Triangle Classifications

• Classification by Congruent Sides

Scalene no congruent sides Isosceles two
congruent sides Equilateral all three sides
congruent.
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Triangle Classifications

• Classification by Congruent Angles.

Acute all angles lt 90º Obtuse One angle
obtuse. Right One right angle. Equiangular All
angles congruent.
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Triangle Classifications

• Classification by Angles.

Maximum Number of Acute Angles in a Maximum
Number of Obtuse Angles in a Right One right
angle. Equiangular All angles congruent m?s60º
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Isosceles Triangle Theorem

• If two sides of a triangle are congruent, then
  the angles opposite those sides are congruent.
• Summary - In other words if you have two
  congruent sides, you have two congruent base
  angles.

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Acute/Right
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Corollary

• Corollary If two angles of one triangle are
  congruent to two angles of another triangle, then
  the third angles are congruent.