2514.sagews

x,y=var('x,y')
f=e^(4*y-x^2-y^2)
plot3d(f,(x,-2,2),(y,0,4),opacity=.8)

x,y=var('x,y')
f=e^(y)*(y^2-x^2)
plot3d(f,(x,-4,4),(y,-3,2),opacity=.8)

x,y=var('x,y')
f=sin(x)*sin(y)
plot3d(f,(x,-pi,pi),(y,-pi,pi),opacity=.8)