How do you calculate area of a square using the length of its diagonal?

"using Pythagoras, you find the length of either of the two sides.

For example, if the diagonal is = 5

Then square it = 25

Then Half it (since both of the other sides of one of the triangles are equal) = 12.5

Then Square Root it = sqrt(12.5)

The length of one side is sqrt(12.5)

So now you can just square it and the area is 12.5

Hope that makes sense"

Actually there are steps here you don't need. Use the equation: A= (d^2)/2 Where d=diagonal length. You don't need to square root it then square it again. That would only make sense if you wanted to find the side length, but in that case all you would have to do is divide the diagonal by the square root of 2, which will also give you the side length, but in a much easier way.