MATH CLASS: My niece, an innocent and trusting young naif, asked me today what exactly a protractor is used for. I tried to explain the utility of the thing, going on in a very long and turgid explanation of the measurement of angles and arcs and there being no royal road to geometry, but it did not clear the matter up to her satisfaction. In fact, she seemed dubious about the whole concept of protractors despite my best efforts to make it crystal clear, the confused child looking at me with the same hard-eyed squint people usually reserve for fast-talking used car salesmen trying to sell them a sample of last year's crop of lemons, until I finally fell back on the explanation I first heard from Billy McGrath in the sixth grade: a protractor is a measuring device that teachers use to make math class seem even longer than it is.