A trickier example of implicitplot.

A deltiod has 3 cusps, making it trickier to get right. The equation (at least in Cartesian cordinates) is also nastier.

> implicitplot( (x^2+y^2)^2 + 8*x*(3*y^2-x^2) + 18*(x^2+y^2) = 27,
x=-10..10,y=-10..10,scaling=constrained,axes=boxed);

Certainly some refining is in order. Note the strange little island down in the lower left corner. Reducing the area of search will help a bit.

> implicitplot( (x^2+y^2)^2 + 8*x*(3*y^2-x^2) + 18*(x^2+y^2) = 27,
x=-1.5..3,y=-2.5..2.5,scaling=constrained,axes=boxed);

Better, but not perfect. One obvious problem is that the "nose" at the right is being cut off, because we aren't testing points on the -axis. This can be remedied by specifying a finer grid, but with an odd number of points.

> implicitplot( (x^2+y^2)^2 + 8*x*(3*y^2-x^2) + 18*(x^2+y^2) = 27,
x=-1.5..3,y=-2.5..2.5,grid=[75,75],scaling=constrained,axes=boxed);

Much, much better.