Curious gifts for thoughtful people

Heart Curve Card

£2.95

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Because it's not real love until you've plotted it on a chart. These are cardioids and other heart-like curves produced by the equations:
 r(theta)=1-sintheta.
 (x^2+y^2-1)^3-x^2y^3=0.
sintcostln|t|  &  |t|^(0.3)(cost)^(1/2),
 x^2+[y-(2(x^2+|x|-6))/(3(x^2+|x|+2))]^2=36
 r(theta)=2-2sintheta+sintheta(sqrt(|costheta|))/(sintheta+1.4)
16sin^3t  &  13cost-5cos(2t)-2cos(3t)-cos(4t).

...as you know.

Measures 18 x 13 cm.
Comes with bright blue envelope.
Blank inside.