Astroid - A Classical Construction

Classical construction of the astroid as a locus.[br][br]To generate the locus, move point [math]A[/math] along the circle, or use the animation button on top right of the app.

Ellipse as Envelope - Correspondence Method

Consider the function [math]f\left(x\right)=\frac{1}{x}[/math] . [br]Represent domain and range of this function respectively over two parallel reference axes.[br]The segments that join each point of the domain with the corresponding point of the range are the envelope of an ellipse.[br][br]Use the sliders [i][color=#a64d79]distance[/color][/i] and [math]O'[/math] to change the distance between axes and the relative position of the Origin points on the two axes.

Pelecoid

Viviani's Window

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