Question

Find the length of the side of a square whose diagonals are 20.

Answer 1

now ABC is right triangle and as it is square so x=y
use Pythagoras theorem for right triangle you'll get..
x^2 + y^2 = 20^2
as x=y so you can write
x^2 + x^2 = 400 (replaced "y" with "x" as both are same)
2x^2 = 400
x^2 = 400/2
x^2 = 200
x = sqrt (200)