Parallelogram Verification: Quadrilateral with Sides 15 and Diagonals 10

Parallelogram Verification with Diagonal Measurements

Shown below is the quadrilateral ABCD.

AB = 15 and CD = 15.

BD = 10 and AC = 10.

AAABBBDDDCCC15101015

Is the quadrilateral a parallelogram?

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Is the quadrilateral a parallelogram?
00:03 A parallelogram is a quadrilateral with 2 pairs of equal opposite sides
00:07 Let's check the sides of our quadrilateral
00:11 We found 2 pairs of equal opposite sides, therefore it's a parallelogram
00:14 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Shown below is the quadrilateral ABCD.

AB = 15 and CD = 15.

BD = 10 and AC = 10.

AAABBBDDDCCC15101015

Is the quadrilateral a parallelogram?

2

Step-by-step solution

To determine if quadrilateral ABCD is a parallelogram, we need to use the property that for a quadrilateral to be a parallelogram, both pairs of opposite sides must be congruent.

The given measurements are:

  • AB = 15
  • CD = 15
  • BD = 10
  • AC = 10

Check the congruency of opposite sides:

  • AB and CD are opposite sides: AB=CD=15 AB = CD = 15
  • For diagonals AC and BD, their lengths do not affect our conclusion concerning sides, though we see diagonals lengths as equal, this extra fact isn't of consequence in this specific theorem application.

Since both pairs of sides AB and CD are equal, and as per the theorem that if opposite sides of a quadrilateral are congruent, then the quadrilateral is a parallelogram, ABCD is a parallelogram.

Therefore, we determine that the solution to the problem is Yes.

3

Final Answer

Yes.

Key Points to Remember

Essential concepts to master this topic
  • Definition: Parallelogram has opposite sides equal and parallel
  • Technique: Check AB = CD (15) and BC = AD
  • Check: Verify both pairs of opposite sides are congruent ✓

Common Mistakes

Avoid these frequent errors
  • Using diagonal lengths to determine side properties
    Don't use diagonal measurements (AC = 10, BD = 10) to conclude opposite sides are equal = wrong reasoning! Equal diagonals don't guarantee a parallelogram. Always check that opposite sides AB = CD and BC = AD are congruent.

Practice Quiz

Test your knowledge with interactive questions

Shown below is the quadrilateral ABCD.

AB = 15 and CD = 13.

BD = 6 and AC = 4

AAABBBDDDCCC134615

Is it possible to conclude that this quadrilateral is a parallelogram?

FAQ

Everything you need to know about this question

Do equal diagonals mean it's a parallelogram?

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No! Equal diagonals (AC = BD = 10) don't guarantee a parallelogram. You need opposite sides to be equal. Equal diagonals actually suggest it might be a rectangle or isosceles trapezoid.

What information do I actually need to verify a parallelogram?

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You need to check that both pairs of opposite sides are congruent: AB = CD and BC = AD. From the problem, we know AB = CD = 15, but we'd need BC and AD lengths too for complete verification.

Is the given information enough to prove it's a parallelogram?

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Not completely! We only know AB = CD = 15, which shows one pair of opposite sides are equal. We need information about BC and AD to fully prove it's a parallelogram.

What other methods can prove a quadrilateral is a parallelogram?

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  • Opposite sides parallel: AB || CD and BC || AD
  • Opposite angles equal: ∠A = ∠C and ∠B = ∠D
  • Diagonals bisect each other: They meet at their midpoints

Why does the explanation say the answer is 'Yes'?

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The explanation assumes we have enough information, but it's actually incomplete. In a real test, you'd need all four side lengths or other properties to definitively prove it's a parallelogram.

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