We have to find the lengths of the diagonals KM and JL: d ( KM ) = √ (( - a - b )² + ( 0 - c )²) = √ (( a + b )² + c² ) d ( JL ) = √ ( ( a - ( - b ) )² + ( 0 - c )²) = √ ( ( a + b )² + c² ) So the lengths of the diagonals KM and JL are congruent. The lengths of the diagonals of the isosceles trapezoid are congruent.
