This tapering is parabolic, it means that every centimeter (or inch) the thickness of the leaf decreases in an amount that relates to the square function of it's length.
Lokhu kudweba kuyinto efanekisayo, kusho ukuthi isentimitha ngalinye (noma intshi) ukushuba kweqabunga kuncipha ngenani elihlobene nomsebenzi wesikwele wobude balo.