The deltoid as a locus or an envelope
- Author:
- Andy Tharratt
The deltoid as a locus or an envelope.
Moving the point labelled 'Movable' produces a deltoid seen as the locus of a point on the small (radius a) or medium (radius 2a) circles as they roll inside the large (radius 3a) circle, or, alternatively, as the envelope of the pink tangent line (which is a diameter of the medium circle of fixed length 4a).