# The diagonal of a square is sqrt 84. What is the area of the square.

The diagonal of a square is the hypotenuse of a 45-45-90 triangle.

In a 45-45-90 triangle the hypotenuse is the leg multiplied by `sqrt(2).`

Therefore, if given the hypotenuse, divide by `sqrt(2)`  to find the length of the leg.

`sqrt(84)/sqrt(2) =sqrt(42)`

Therefore each side of the square is `sqrt(42).`

To find the...

Start your 48-hour free trial to unlock this answer and thousands more. Enjoy eNotes ad-free and cancel anytime.

The diagonal of a square is the hypotenuse of a 45-45-90 triangle.

In a 45-45-90 triangle the hypotenuse is the leg multiplied by `sqrt(2).`

Therefore, if given the hypotenuse, divide by `sqrt(2)`  to find the length of the leg.

`sqrt(84)/sqrt(2) =sqrt(42)`

Therefore each side of the square is `sqrt(42).`

To find the area of the square:  `A=s^2.`

`A = (sqrt(42))^2`

Therefore the area of the square is: `42 u^2`

Approved by eNotes Editorial Team

The length of the diagonal of a square with side S is equal to `sqrt(S^2 + S^2)` = `S*sqrt 2` .

If the diagonal of a square is D, the length of the side is `D/sqrt 2`

A square has a diagonal of length `sqrt 84` . The area of the square is `(sqrt 84)^2/2 = 84/2 = 42`

The area of the square is 42 square units.

Approved by eNotes Editorial Team