abcd is a parallelogram.if the two diagonals are equal.find the measure of angle abc

ABCD is a parallelogram in which as you can see the diagonals are equal. According to properties of paralleograms this is true only when the parallelogram is a rectangle.

Now as ABCD is a rectangle all its angles are equal to 90º

Hence, angle ABC=90º

If the diagonals are not of equal length ABCD would not be a rectangle

**
**