+4 The vertex of the right isosceles triangle is the center of the square. What is the area of the overlapping region?
[asy]
draw((-1,-1)--(1,-1)--(1,1)--(-1,1)--cycle);
draw(sqrt(3)*dir(30)--sqrt(3)*dir(-60)--(0,0)--cycle);
draw(.25*dir(30)--.25*(dir(30)+dir(-60))--.25*dir(-60));
label("10",(-1,0),W);
dot((0,0));
[/asy]
