The Mathematical Evolution of the Heart

There are a number of mathematical curves that produce heart shapes. Here are some of them. Equations of these curves are (in order of appearance) : (1) r = 1 - sin θ (polar) (2) x² [y - (2(x² |x| - 6))/(3(x² |x| 2))]² = 36 (3) (x² y² - 1)³ - x²y³ = 0 (4) r = 2 - 2sin θ sin θ√|cos θ|/(sin θ 1.4) (polar) (5) x = 16sin³ t, y = 13cos t - 5cos 2t - 2cos 3t -cos 4t (parametric) (6) y = (cos 200x.√cos x √|x| - 0.7)(4 - x²)^