Question

If two sides of a pair of opposite sides of a cyclic quadrilateral are equal, proof that its diagonals are equal

Answer 1

Remember sum of opposite angles in a cyclic quadrilateral is 180 degree.

Construct a diagonal.
The 2 traingles formed will be congruent.
So opposite angles are equal.

Hence All angles are 90 degrees.

So it is a rectangle...
So, Diagonals are equal because in a rectangle Diagonals are equal