połowa stożka; dimidius conus
VITELO Opt. p. 154 : erunt ... arcus ... circulorum minores semicirculis suis, ergo portio uisa minor erit h-o, quoniam sicut tota conuexa superficies pyramidis toti basi respondet, sic pars proportionalis ad totam conuexam superficiem parti proportionali basis ad totam basim.