Question

Prove that if a quadrilateral has four equal sides and one right angle, then the quadrilateral is a square

Answer 1

so lets ABCD are the sides of the square and AB=CD, AC=BD and the Angle ABC = 90 so therefore by making a diagonal we can use the SAS or SSS congruency for two triangles, so we can prove two triangles are equal and that is why the shape is square.