# Very strange of Mathematica!

The following two expressions are the same when checked numerically.

``fun1[x_, y_] =    1/4 (Sqrt[(1 - y)/(       4 + y (-4 + (1 - 2 x)^2 y))] (2 - y + Sqrt[         4 + y (-4 + (1 - 2 x)^2 y)]) -       2 ((-1 + 2 x) y + Sqrt[         4 + y (-4 + (1 - 2 x)^2 y)]) Sqrt[-(((-1 + y) (-2 + y + Sqrt[           4 + y (-4 + (1 - 2 x)^2 y)])^2)/(4 -           4 y + ((-1 + 2 x) y + Sqrt[            4 + y (-4 + (1 - 2 x)^2 y)])^2)^2)]); fun2[x_, y_] = Sqrt[1 - y]/2; ``

However, Mathematica is not able to reduce `fun1[x,y]` to `fun2[x,y]`, with `Simplify` of `FullSimplify`. Is there any way of doing this simplification? Also note that $$0\le x \le 1$$ and $$0\le y\le 1$$.