Inscribed angle theorems exist for ellipses, hyperbolas and parabolas, too. The constructions for hyperbolas and parabolas are similar. There are three primary types of conic sections&colon; ellipses (including circles), parabolas, and hyperbolas. Steiner generation can also be defined for hyperbolas and parabolas. An alternative way uses the "inscribed angle theorem" for parabolas. The angular properties described above follow immediately from the functional form of the parabolas. He discovered a way to solve the problem of doubling the cube using parabolas. This reflective property is the basis of many practical uses of parabolas. Parabolas can open up, down, left, right, or in some other arbitrary direction. Since all parabolas are similar, this simple case represents all others. Both parabolas are cut at B and A respectively.