Given: a rhombus is a quadrilateral with 4 congruent sides. prove: if quadrilateral abcd does not have 4 congruent sides, then it is not a rhombus. determine the first step to prove this statement using proof by contradiction.

A rhombus is by definition a quadrilateral all of whose sides are congruent (have the exact same length). To prove by contradiction, you have to assume that a quadrilateral ABCD does not have 4 congruent sides and is a rhombus, because that is against the definition.