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Summary
DescriptionTrefoilKnotOrder2Symmetry.png
English: The common visualizations of the trefoil knot exhibit its order-3 rotational symmetry (by 120 degrees). But this knot also has two order-2 rotational symmetries (by 180 degrees): (a) about the axis perpendicular to the plane, through the center, and (b) about the Y-axis (i.e., a reflection in the Y-axis followed by flipping all over-under crossings).
The diagram consists of two semicircles (radius 1+√2, centered at (0,1) and (0,-1)) and four 3/8 circles (radius 1, centered at (1,1), (-1,1), (-1,-1), and (1,-1)) that connect smoothly, with three appropriate under-over crossings.
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