Assertion: isometry | /r/HasProperty | a combination of a rotation
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Source sentences:
text: all isometries which are a combination of a rotation about some axis and a proportional translation along the axis; in general this is combined with k -fold rotational isometries about the same axis ( k ≥ 1 ); the set of images of a point under the isometries is a k -fold helix; in addition there may be a 2-fold rotation about a perpendicularly intersecting axis, and hence a k -fold helix of such axes.