  It is well-known to be impossible to trisect an arbitrary angle and duplicate
an arbitrary cube by a ruler and a compass. On the other hand, it is known from
the ancient times that these constructions can be performed when it is allowed
to use several conic curves. In this paper, we prove that any point
constructible from conics can be constructed using a ruler and a compass,
together with a single fixed non-degenerate conic different from a circle.
