> This shape, called a hyperboloid, minimizes the amount of material required to build it I guess that to build it "for its required purpose" is implicit in t

> This shape, called a hyperboloid, minimizes the amount of material required to build it I guess that to build it "for its required purpose" is implicit in the sentence. I agree, that the author could have gone into more detail of what are the requirements of cooling towers but that may be out of the scope of the article.