# 7.4.1f(x,y)=x^2+y-2f(0.5,0.5)plot3d(f,(x,0.4,.6),(y,0.4,0.6))+point3d([0.5,0.5,-1.25],size=20,color="red")# Yep, curved surface looks like plane when you zoom in!

-1.25000000000000

3D rendering not yet implemented

# 7.4.3# cutting plane for Y = 2 intersecting surface Z = X^2/2 - Y^2/4 - 4# Z = X^2/2 - 2^2/4 - 4 = X^2/2 - 1 - 4 = X^2/2 - 5var("X")plot(X^2/2-5,(X,-2,2),axes_labels=["X","Z"])