Question

ABCD is a parallelogram such that its diagonals are equal.What is the measure of angle ABC?

Answer 1

In a parallelogram if two diagonals are equal, then the parallelogram is a rectangle.So, ABCD is a rectangle.It is known that each interior angle of a rectangle is 90 degree.Since ABC is an interior angle of rectangle ABCD, so measure of angle ABC is 90 degree