Triangles and Angles

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Section 4-1

• Triangles and Angles

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triangle

• A figure formed by three segments jining three
  noncollinear points.

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Triangles are classified by their sides and
angles.
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Side Classification

• Equilateral Triangle 3 congruent sides
• Isosceles Triangle at least 2 congruent sides
• Scalene Triangle No congruent sides

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Isosceles Triangle
Equilateral Triangle
Scalene Triangle
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Angle Classification

• Acute Triangle 3 acute angles
• Equiangular Triangle 3 congruent angles
• Right Triangle 1 right angle
• Obtuse Triangle 1 obtuse angle

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Acute Triangle
Right Triangle
Obtuse Triangle
Equiangular Triangle
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When naming a triangle you must be as specific as
possible!
Name triangles by BOTH sides and angles!
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Some Examples
1.
Equilateral Equiangular
2.
Obtuse Isosceles
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Parts of a triangle

• The segments are called the sides of a triangle
• Each of the three points is a vertex of the
  triangle
• Two sides sharing a common vertex are adjacent
  sides

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Sides
Vertices A, B, C
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Parts of a right triangle

• Leg the sides that form the right angle
• Hypotenuse the side opposite the right angle
  (longest side)

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Hypotenuse
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Parts of an isosceles triangle
When it has only two congruent sides

• Leg two congruent sides
• Base the 3rd side

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Base