Hi Andre.
It sounds like you've run into a peculiarity in the English usage of the word "trapezoid". As
Chris wrote in this earlier reply, the North American and British definitions are switched:

North American definition 
British definition 
trapezoid 
a quadrilateral plane figure having two parallel and two nonparallel sides 
any rectilinear quadrilateral plane figure with no parallel sides 
trapezium 
any rectilinear quadrilateral plane figure with no parallel sides 
a quadrilateral plane figure having two parallel and two nonparallel sides 
Note that none of these definitions say anything about the lengths of the sides, parallel or not, so you should be able to create a trapezoid (trapezium) with a right angle under any definition.
Stephen La Rocque. >
