A square has sides that are each 90 feet long. Which equations can be used to calculate d, the length of a diagonal on a square, in feet?

The length of a diagonal on a square represents a hypotenuse of the right triangle whose legs are equal

And also this triangle is a half of the square

The length of one side of a square = 90 feet

∴ d² = 90² + 90² = 2 * 90²

∴ d = 90√2

∴ The equations can be used to calculate d = 90√2

In general for any square has length of side = x

The diagonal of the square = d = x√2