Shodor > Interactivate > Discussions > Trapezoids

Mentor: There is one more family of quadrilaterals that we need to talk about. I need to tell you about trapezoids. Trapezoids have exactly one pair of opposite sides that are parallel.

Student: Are those opposite sides congruent too?

Mentor: They don't have to be. A trapezoid can look like this:

Student: Oh, so the other sides can look any way that you want them to?

Mentor: Right. However, the other sides cannot be parallel because we say that trapezoids have exactly one pair of parallel sides.

Student: Yeah, because if it had 2 pairs of parallel sides then it would be a parallelogram!

Mentor: That's very perceptive of you! Do you all remember what we called a triangle that had two congruent sides?

Student: That's an isosceles triangle.

Mentor: Right. So what do you think we call a trapezoid in which the two non-parallel sides are congruent?

Student: An isosceles trapezoid?

Mentor: Very good! Can you draw one of those?

Student: I think it would look like this:

Mentor: Very nice. Does everyone understand what trapezoids are now? You know many types of quadrilaterals now!

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