CISSEY, se's!', ERNEST LOUIS OCTAVE COUR TV!' (1811-82). A French general. He was born in Paris. and was educated at the school of Saint Cyr. !laving served with distinction in Algeria and the Crimea, lie was paunoted in 1863 to be general of a division. He fought in the Franco German War. and in the contest against the Commune of 1871. After being elected to the National Assembly (February, 1871), he was Minister of War from 1871 to 1873 and in 1S74 76. He was elected life Senator in 1575.
CIS'SOID kissoeides, like ivy, from Kto-a6g, kissos, ivy + Eictog, cidos, shape, form). Au ivy-like curve, first studied by Diodes, about n.c..180. The commentary of Diodes sets forth the definition of the eissoid, which in modern notation will be understood from the figure. The ordinates Ili an' are equidistant from the centre e, and the line lint cuts nn' in 1''. a point On the eissoid. A more general construction is the following: Draw any line OR from 0 to Nit, and take RP = OS. Then I' will be a point on the curve. The Carte 3 sian equation of this curve is and the polar equation is r = 2a tan 0 sin 0. (See ANALYTIC GEOMETRY.) The eurve passes through the points (a, a) and (a, a), is symmetric with respect to the X-axis, and lies I ctween the axis (x=0) and the asymptote XR. whose equa
tion = 2a : the origin is a cusp of the first specie:. (See CURVES.) II IlygellA expressed the length of an are of this eurve limited by any two points (reetified it) in 1651. The area of the .pace included between the t WO branches and their asymptote was first given by Fermat (1661) ; it is equal to three times the area of the generating circle. If, instead of the circle, any other curve is taken as the generatrix, the result ing curve is called cissoidal. The eissoid is the pedal (see Cunv•s) of a parabola with respect to the vertex. This curve has been used in solving two famous problems of antiquity—the construc tion of two geometric means between two seg ments, and the duplication of the cube (q.v.).
: Klein. 1 rage u syetrah Itc Fragen der ElemeniUrgeometric (Leipzig, 1595) ; trans lated by Boman and Smith, Famous Problems of Elementary Geometry (ito,(on, 1894): Cow, Ilistory of Grcek Mathematics (Cambridge, 1884).