Proving Lines Parallel Flashcards

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Questions and Answers

Given: AB // DC and m∠2 ≅ m∠4. Prove: AD // BC. What is the equation that justifies this?

  • m∠1 + m∠4 = 180° (correct)
  • m∠1 + m∠2 = 180°
  • m∠3 + m∠4 = 360°
  • m∠2 + m∠4 = 90°

Which lines are parallel? Justify your answer based on angles (110,110,80).

Lines a and b are parallel because their corresponding angles are congruent.

In the diagram, if g ∥ h, m∠1 = (4x + 36)°, and m∠2 = (3x - 3)°, what is the measure of ∠3?

60

Parallel lines e and f are cut by transversal b. What is the value of x?

<p>25</p> Signup and view all the answers

Which diagram shows lines that must be parallel when cut by a transversal?

<p>B (91, 91) (C)</p> Signup and view all the answers

Parallel lines e and f are cut by transversal b. What is the value of y?

<p>130</p> Signup and view all the answers

Which lines are parallel? Justify your answer based on angles (75, 75, 115).

<p>Lines e and f are parallel because their alternate exterior angles are congruent.</p> Signup and view all the answers

Lines c and d are parallel, cut by transversal p. What must be true by the corresponding angles theorem?

<p>∠2 ≅ ∠6</p> Signup and view all the answers

Which equation is enough information to prove that lines m and n are parallel when cut by transversal p?

<p>All of the above (D)</p> Signup and view all the answers

Which set of equations is enough information to prove that lines a and b are parallel when cut by transversal f?

<p>m∠1 = 110° and m∠3 = 70° (D)</p> Signup and view all the answers

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Study Notes

Proving Lines Parallel

  • To prove lines are parallel, analyze angle relationships formed by transversals.
  • If m∠1 + m∠4 = 180°, then lines AB and DC are parallel (AB // DC).
  • If corresponding angles are congruent, lines are parallel (e.g., m∠2 ≅ m∠4 implies AD // BC).

Angle Relationships and Properties

  • In parallel line configurations, alternate exterior angles congruence indicates parallel lines (e.g., lines e and f confirmed as parallel due to congruent angles).
  • When two lines are parallel and cut by a transversal, corresponding angles are equal (e.g., ∠2 ≅ ∠6).

Solving Angle Measures

  • Given angle equations can help determine angle measures and values for variables (e.g., m∠1 = (4x + 36)° and m∠2 = (3x - 3)° leads to m∠3 = 60°).
  • Example solving: If parallel lines yield x = 25, and y = 130 from angle measures formed by transversals.

Justifying Parallel Lines

  • Parallel lines can be justified through congruent angle pairs (e.g., alternate interior, corresponding, or same-side interior angles).
  • Various angle equations can confirm whether lines are parallel; for instance, a = d, c = d, and b + d = 180° are sufficient to prove m and n are parallel.

Identifying Parallel Lines in Diagrams

  • Recognize patterns in diagrams where transversals intersect parallel lines, checking for congruent angles to assert parallelism.
  • In conjunction scenarios, multiple angles being equal can signify the same conclusion (e.g., lines a and b being parallel from m∠1 = 110° and m∠3 = 70°).

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