| Answer | Crossword Clue |
|---|---|
| envelope | curve tangent to each of a family of curves |
| envelopes | A curve or surface tangent to each of a family of curves or surfaces |
| envelope | surface tangent to each of a family of surfaces |
| crunode | a point at which two branches of a curve intersect, each branch having a distinct tangent; node |
| trajectories | A curve or surface cutting a family of curves or surfaces at a constant angle |
| trajectory | A curve or surface cutting a family of curves or surfaces at a constant angle |
