What if I showed angles DEB and EBC to be equall

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Discussion Overview

The discussion revolves around proving that quadrilateral BCDE is a trapezium, with a focus on the angles DEB and EBC in the context of a regular pentagon ABCDE. Participants explore different approaches to demonstrate the necessary conditions for BCDE to qualify as a trapezium.

Discussion Character

  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant suggests that showing angles DEB and EBC are equal could prove that BCDE is a trapezium.
  • Another participant proposes demonstrating that lines EB and DC are parallel as a method to establish the trapezium condition.
  • A different viewpoint emphasizes that a trapezium requires two sides to be parallel, and suggests using alternate angles to prove this condition.
  • Some participants express uncertainty regarding the definition of a trapezium, with one noting that sources vary on whether the other two sides must be non-parallel.
  • One participant reiterates that proving one pair of sides parallel is sufficient to classify the shape as a trapezium, referencing definitions from various sources.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the definition of a trapezium and the conditions required to prove that BCDE is one. Multiple competing views regarding the necessary properties of trapeziums remain present in the discussion.

Contextual Notes

There are ambiguities in the definitions of trapeziums and trapezoids as referenced by different sources, leading to varying interpretations of the conditions necessary for classification.

m00c0w
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http://img298.echo.cx/img298/2145/pentagon8zw.png ABCDE is a regular pentagon, in the previous question I worked out angle AEB to be 36°.. the next question has asked to prove that BCDE is a trapezium but I don't know how to. I figured it might be to do with showing that the sum of the angles in BCDE = 360° but that doesn't necessarily prove it is a trapezium. What if I showed angles DEB and EBC to be equal.. does that prove it?

Many thanks.
 
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You want to show that lines EB and DC are parallel. One way: pick a point F to the left of D along line CD, and show DEB = EDF.
 
hello there

a trapezium needs to have two sides parallel to each other and the other two sides unparallel to each other, if you want you could draw diagnals through the trapezium and prove that the alternate angles are equal that is prove that angle EBD= BDC
or anything similar to prove that it has two parallel sides

check out this simple link
http://www.icteachers.co.uk/children/sats/quadrilaterals.htm

Steven
 
I have never heard that a trapezoid (trapezium) had to have the other two sides non-parallel. Mathworld and dictionary.com are ambiguous but wikipedia is clear that a trapezoid can also be a parallelogram.
http://en.wikipedia.org/wiki/Trapezoid
 
BicycleTree said:
I have never heard that a trapezoid (trapezium) had to have the other two sides non-parallel. Mathworld and dictionary.com are ambiguous but wikipedia is clear that a trapezoid can also be a parallelogram.
http://en.wikipedia.org/wiki/Trapezoid


I knew i should have not erased what i originally wrote, well anyway i provided the link so that he doesn't get confused, well such a shape has a proper name a parallelogram which is a part of the family of quadrilaterals, and in this case all that is necessary is to prove that it has one pair of parallel sides to show that it is a trapezium
 

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