For a given curve , consider the locus of the point
from where the tangents
from
to
meet at a fixed given angle.
This is called an isoptic curve of the given curve.
| curve | isoptic |
| cycloid | curtate or prolate cycloid |
| epicycloid | epitrochoid |
| hypocycloid | hypotrochoid |
| parabola | hyperbola |
| sinusoidal spiral | sinusoidal spiral |