The Joy of Mathematics

Title: Astroid, Attempt 2
Description: x = 3cos(q) + cos(3q); y = 3sin(q) + sin(3q)
Equation: z = (4x³/r³ - x) + (4y/r - 6y³/r³ - y)
Drawing Limits: (-2, -2) - (2, 2)
Min z: -2.63133, Max z: 2.63129