EntityQ1188048· pop 15· linked from 15 articlesBarbier's theoremSign in to savetheorem that every curve of constant width has perimeter π times its widthConnectionsgeometryEntityPiConceptInternational Standard Book NumberEntitycircleEntitydiameterEntityradiusEntitydigital object identifierEntityperimeterEntitycurveEntityJames Joseph SylvesterEntityQ22908627EntityReuleaux triangleEntitycentral angleEntitysurface of revolutionEntityMathematical ReviewsEntityCiteSeerXEntityisoperimetric inequalityEntityunit sphereEntityMinkowski additionEntityintegral geometryEntityCategoriesConstant widthLengthPiTheorems in plane geometry