Question

the diagonal of a square field is 90 m.what is its area

Answer 1

Diagonal=(a)²+(a)²
where a=side of diagonal
since diagonal=90 
just put that in the above equation and find "a".
Then find the area using formula "a²"

Answer 2

Let the side of the square field be 'x'

Diagonal²=x²+x²
90²=2x²
8100=2x²
4050=x²

Area of square field= x*x
=x²
=4050 m²