ABCD is a square If BD 5 what is the area of square?

The square on the hypoteneuse of a right-triangle is equal to the sum of the squares on the two adjacent sides.

So. 5 units by 5 units = 25 square units

25 is therefore the sum of the squares on BC and CD.

As these sides are equal, we know that each square must be 12.5 square units.

The length of the sides of a square containing 12.5 square units is the square root of 12.5.

That is equal to 3.5355 (correct to four decimal places.

So, each side of the square is 3.5355 units long.