VISIERA Curve studied by Agnesi (1718-1799). Visiera: visor in Italian. The name visiera was given by Peano in 1887, probably by analogy with versiera.

 Polar equation: . Cartesian equation: .  Right rational circular cubic with an isolated point (-> Sluze cubic)

The visiera is the antihyperbolism of the versiera with respect to its base and the symmetric image of its vertex with respect to its base; in the above equation, the visiera is the antihyperbolism with respect to O and x = a of the versiera: .

Like all rational circular cubics, the visiera can be defined as:
- The cissoid of a circle and a tangent at A to this circle, with pole O, the point diametrically opposed to A (here, A(0,2a)). - The pedal of a parabola with respect to the symmetric image of the vertex about the focus (here, the parabola with vertex A and focus F(0,a)). - The inverse of an ellipse with eccentricity with respect to one of its secondary summits (here, the ellipse ). And, like all right rational circular cubic, it can be constructed

 - by the Newton set-square method: - by the Kiernan construction:  Do not mistake the visiera for the conchoid of Nicomedes.