The equations of the diagonals of square formed by lines x=0, y=0, x= 1, and y=1 are

The coordinates of the vertices of the square ate A(0, 0),B(0, 1), C(1, 1), and D(1, 0).Now, the equation of AC is y=xand that of BD is y−1=−11(x−0)or  x+y=1