Inequalities in Geometry

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Chapter 6

• Inequalities in Geometry

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SECTION 6-1

• Inequalities

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THEOREM 6-1

• The measure of an exterior angle of a triangle is
  greater than the measure of either remote
  interior angle

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SECTION 6-2

• Inverse and Contrapositives

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Inverse

• Statement if p, then q
• If not p, then not q

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Contrapositive

• Statement if p, then q
• If not q, then not p

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Venn Diagram

• A visual tool to represent a conditional

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Logically Equivalent

• A conditional and its contrapositive statement

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SECTION 6-3

• Indirect Proof

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How to Write an Indirect Proof

• Assume temporarily that the conclusion is not
  true.
• Reason logically until you reach a contradiction
  of a known fact.
• Point out that the temporary assumption must be
  false, and that the conclusion must then be true

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SECTION 6-4

• Inequalities for One Trianlge

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THEOREM 6-2

• If one side of a triangle is longer than a second
  side, then the angle opposite the first side is
  larger than the angle opposite the second side

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THEOREM 6-3

• If one angle of a triangle is larger than a
  second angle, then the side opposite the first
  angle is longer than the side opposite the second
  angle

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COROLLARY 1

• The perpendicular segment from a point to a line
  is the shortest segment from the point to the line

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COROLLARY 2

• The perpendicular segment from a point to a plane
  is the shortest segment from the point to the
  plane.

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THEOREM 6-4

• The sum of the lengths of any two sides of a
  triangle is greater than the length of the third
  side.

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SECTION 6-5

• Inequalities for Two Triangles

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THEOREM 6-5

• If two sides of one triangle are congruent to two
  sides of another triangle, but the included angle
  of the first triangle is larger than the included
  angle of the second, then the third side of the
  first triangle is longer than the third side of
  the second triangle.

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THEOREM 6-6

• If two sides of one triangle are congruent to two
  sides of another triangle, but the third side of
  the first triangle is longer than the third side
  of the second, then the included angle of the
  first triangle is larger than the included angle
  of the second triangle.

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• THE END