# Spiky Feathers and Geometric Fish

The astroid curve is an example of a hypocycloid – a curve generated by rotating a fixed point on a small circle around a larger circle. Specifically, it is a hypocycloid with four cusps.

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# Parametric T-shirts

I’m excited to share my new TeeMill site, selling T-shirts based on graphs of parametric equations.

There are three designs currently available, and all can be bought in loose fit or fitted, and with or without the equations that created the design displayed underneath.

You can also find GeoGebra files, where you can play with the graphs of the equations yourself, here.

# Spin, Laugh and Dance

I’d like to introduce you to the graph of $x=\sin(f_1t)e^{d_1t}$, $y=\sin(f_2t)e^{d_2t}$, a curve that spins, laughs and dances.

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