Answer:
50
Explanation:
Diagonal of square = 10
Use special triangles to find the area because a square's diagonal divides the 90 degree angles into 45 degrees
45-45-90 triangle
x : x : x√2
1 : 1 : 10
10=x√2
10/√2=x, rationalize denominator and you get 5√2 as the square's side length
Area is s^2, s being the length of a side
(5√2)^2=25*2=50