Geometry Direct and Indirect Proofs
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Questions and Answers

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

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

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

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

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

    Which property of equality justifies that 4 = 4?

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

    In a direct proof, you assume the ______ is true and use properties, postulates, definitions, and theorems to show the ______ is true.

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    If $a = b$ and $b = c$, what property of equality allows us to conclude that $a = c$ ?

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

    If $x = 7$, what property of equality justifies replacing $x$ with 7 in the equation $x + y = 12$?

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

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

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

    Flashcards

    Direct Proof

    A method of proof that starts with givens and uses logical steps to arrive at the conclusion.

    Indirect Proof

    A method of proof that assumes the opposite of what you want to prove, and then shows this assumption leads to a contradiction.

    Midpoint

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

    Congruent Segments

    Segments that have the same length.

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    Reflexive Property

    A quantity is always 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 a can replace b in any equation.

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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 a * c = b * c

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    Division Property

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

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    Simplification

    Making an equation simpler by combining like terms or performing an operation.

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    Two-Column Proof

    A proof organized into statements and reasons in two columns.

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    Paragraph Proof

    A proof presented in a paragraph format.

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    Given

    Information provided to start a proof.

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    Prove

    The statement you are trying to demonstrate as true.

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    Proof

    A valid argument showing a statement is true or false.

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    Study Notes

    Direct Proof

    • A direct proof starts with a premise (p) and aims to prove a conclusion (q) is true.
    • It assumes p is true and uses postulates, definitions, and theorems of geometry to show q is true.
    • The process typically involves steps like stating the given, stating what needs to be proven, drawing a diagram as a guide, and presenting the proof in a structured way (paragraph, two-column, or flow chart).

    Writing a Direct Proof

    • State the given: The given information is considered a fact.
    • State what to prove: This is the desired conclusion.
    • Draw a figure: This serves as a visual aid.
    • Present the proof: Use a preferred method (paragraph form, two-column form, flow chart).

    Indirect Proof

    • Begins by assuming the conclusion (q) is false.
    • Then, using the same properties, postulates, definitions, and theorems, show that the premise (p) is also false.
    • This leads to a contradiction, confirming the original conclusion was correct.

    Writing an Indirect Proof

    • Accept the given statement is true: Start with the given information.
    • Assume the opposite of the statement to be proved: Assume the conclusion is false.
    • State the reason directly until there is a contradiction: Use logic and known facts to reach a contradiction
    • State that the assumption of the opposite statement to be proved must be false: This confirms the original conclusion.
    • Draw a figure: (Optional) for visual clarity.
    • Present the proof: Use a chosen method.

    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 ac = bc.
    • Division Property: If a = b and c ≠ 0, then a/c = b/c.
    • Substitution Property: If a = b, then b can replace a in any expression or equation.

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    Related Documents

    Direct and Indirect Proof PDF

    Description

    This quiz covers the concepts of direct and indirect proofs in geometry. It outlines the steps for writing both types of proofs, emphasizing the importance of premises, conclusions, and visual aids. Test your understanding of how to structure and present geometric proofs effectively.

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