Question

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.

Answer 1

Assume ABCD does not have 4 congruent sides and is a rhombus

Answer 2

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.