Good day everyone, i am new here and i found this site very useful. I am not a mathematician but i really want to learn math. Can anyone please give me ideas on how to prove this?

A Circumscribable quadrilateral is inscribable if and only if its area equals the square root of the product of its four sides.

I am really confused on how to start with the proof and the if and only if statement,.,

thnx in advance..