Deltoid
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Parametric Equation : x = a ( 2cos t + cos 2t ) , y = a ( 2sin t - sin 2t ) |
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Parametric Equation : x = a ( 2cos t + cos 2t ) , y = a ( 2sin t - sin 2t ) |
The tricuspoid or deltoid was first considered by Euler in 1745 in connection with an optical problem.
It was also investigated by Steiner in 1856 and is sometimes called Steiner's hypocycloid.