Infinity symbol symbol is encoded in Unicode at and in LaTeX as codice_1: formula_4. The Unicode set of symbols also includes several variant forms of the infinity symbol, that are less frequently available in fonts: , and in block Miscellaneous Mathematical Symbols-B. The acid-free paper symbol mentioned above is encoded separately as . Infinity symbol The infinity symbol (sometimes called the lemniscate) is a mathematical symbol representing the concept of infinity. The shape of a sideways figure eight has a long pedigree; for instance, it appears in the cross of Saint Boniface, wrapped around the bars of a Latin cross. However, John
Duocylinder flat tops. This operation is equivalent to removing select vertices/pyramids from polytopes, but since the 3-sphere is smooth/regular you have to generalize the operation. The dihedral angle between the two 3-d hypersurfaces on either side of the ridge is 90 degrees. Parallel projections of the duocylinder into 3-dimensional space and its cross-sections with 3-dimensional space both form . Perspective projections of the duocylinder form torus-like shapes with the 'doughnut hole' filled in. The duocylinder is the limiting shape of duoprisms as the number of sides in the constituent polygonal prisms approach infinity. The duoprisms therefore serve as good polytopic approximations