Math CentralQuandaries & Queries


Question from Nazrul, a teacher:

How can I draw a trapezoid whose parallel sides and other two sides are given.

Try working backwards: Suppose you are given the trapezoid ABCD with AD parallel to BC and the four sides all having your desired lengths. Draw DC' parallel to AB with C' on BC. Then ABC'D is a parallelogram (with BC' equal in length to AD). That means C'C = CB - AD. Now you know how to work forwards: Start with triangle DC'C with side lengths DC' = AB, C'C = CB - AD, and CD.


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