Mathematical Proofs: Direct and Indirect
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Questions and Answers

Which property of equality states that a quantity is always equal to itself?

  • Transitive Property
  • Reflexive Property (correct)
  • Symmetric Property
  • Addition Property
  • If x = 5, which property of equality justifies that 5 = x?

  • Transitive Property
  • Reflexive Property
  • Substitution Property
  • Symmetric Property (correct)
  • If a = b and b = c, what property of equality allows us to conclude that a = c?

  • Reflexive Property
  • Transitive Property (correct)
  • Addition Property
  • Symmetric Property
  • If x = 7, what property of equality justifies replacing x with 7 in the equation x + y = 12?

    <p>Substitution Property (A)</p> Signup and view all the answers

    Which property of equality is used when we conclude that a + c = b + c from a = b?

    <p>Addition Property (A)</p> Signup and view all the answers

    Given m = n and c = 2, which property of equality justifies that mc = nc?

    <p>Multiplication Property (A)</p> Signup and view all the answers

    What property of equality allows you to conclude that a - d = b - d if a = b?

    <p>Subtraction Property (B)</p> Signup and view all the answers

    Which property of equality allows you to divide both sides of 6p = 18 by 6 to get p = 3?

    <p>Division Property (C)</p> Signup and view all the answers

    If x = y, which property of equality allows you to substitute y for x in the equation x + z = 10?

    <p>Substitution Property (C)</p> Signup and view all the answers

    Which property of equality justifies that 4 = 4?

    <p>Reflexive Property (B)</p> Signup and view all the answers

    Flashcards

    Direct Proof

    A method of proof that assumes a premise is true and uses known rules to show a conclusion is also true.

    Indirect Proof

    A proof method that assumes the conclusion is false and shows this leads to a contradiction, proving the conclusion must be true.

    Midpoint

    A point that divides a line segment into two equal segments.

    Congruent Segments

    Two segments with equal lengths.

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    Reflexive Property

    A quantity is equal to itself.

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    Symmetric Property

    If a = b, then b = a.

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    Transitive Property

    If a = b and b = c, then a = c.

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    Substitution Property

    If a = b, then b can be substituted for a in equations or expressions.

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    Addition Property

    If a = b, then a + c = b + c.

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    Subtraction Property

    If a = b, then a - c = b - c.

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    Multiplication Property

    If a = b, then ac = bc.

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    Division Property

    If a = b and c ≠ 0, then a/c = b/c.

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    Paragraph Proof

    A proof written in a paragraph format explaining each step in detail.

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    Two-column Proof

    A proof presented in two columns: Statements and Reasons.

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    Flowchart Proof

    A visual proof using boxes and arrows to show step-by-step reasoning.

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    Simplification

    Simplifying expressions while maintaining equality.

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    Given

    A statement accepted as true at the start of a proof.

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    Prove

    A statement to be demonstrated as true through proof.

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    Statement (proof)

    A verifiable assertion.

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    Reason (proof)

    Logical justification for the statement.

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    Property of equality

    Rules governing mathematical equations that allow you to transform them without changing the solutions.

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    Study Notes

    Direct Proof

    • A direct proof assumes a premise (p) is true, then uses properties, postulates, definitions, and theorems to show that the conclusion (q) is also true.
    • Steps to write a direct proof:
      • State the given information.
      • State what needs to be proven.
      • Draw a figure (if applicable).
      • Present the proof (paragraph, two-column, or flow chart).

    Indirect Proof

    • An indirect proof assumes the conclusion is false, then uses properties, postulates, definitions, and theorems to show that the premise is also false, leading to a contradiction.
    • Steps to write an indirect proof:
      • Accept the given statement as true.
      • Assume the opposite of the statement to be proved.
      • State the reason directly until there is a contradiction of the given or the assumed statement.
      • State the assumption is false.
      • Draw a figure (if applicable).
      • Present the proof (paragraph, two-column, or flow chart).

    Properties of Equality

    • Reflexive Property: Any quantity is equal to itself (a = a).
    • Symmetric Property: If a = b, then b = a.
    • Transitive Property: If a = b and b = c, then a = c.
    • Addition Property: If a = b, then a + c = b + c.
    • Subtraction Property: If a = b, then a - c = b - c.
    • Multiplication Property: If a = b, then a * c = b * c.
    • Division Property: If a = b and c ≠ 0, then a/c = b/c.
    • Substitution Property: If a = b, then b can be substituted for a in any expression or equation.

    Example Problems/Proofs:

    • Provided example problems illustrate how to apply direct and indirect proofs in geometry, including a proof that the midpoint of a line segment divides it into two congruent segments.

    Activity Questions

    • Questions are designed to test understanding of the different properties of equality.

    Answer Key

    • Correct answers to the activity questions are presented.

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    Related Documents

    Direct and Indirect Proof PDF

    Description

    Explore the techniques of direct and indirect proofs in mathematics. This quiz covers the steps to write each type of proof and the properties of equality. Test your understanding of these fundamental concepts for logical reasoning.

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