"Why should Johnny learn the quadratic equation? He'll never use it." Did the spectators at those Renaissance polynomial-solving contests grasp the motivation of the problem? What is the most "mundane" (whatever that means) need for solving a cubic? SteveG's irrational(!) remark could be phrased: 1) Two blips on the radar are exactly a mile away and 40 deg apart. How far apart are they? Another one: 2) A cupcake paper is made from a 6" disk. What conical frustum maximizes its batter capacity? The terser "What's the largest capacity pie tin you can make from a square foot of sheet metal?" is only biquadratic. Unless I've erred, it's 12.06" across, 2.89" deep, with only a 5.46" bottom, and holds a human blood supply(!?) (6.02qt). According to the prism(at)oid volume formula (Simpson's rule, which is exact in this case), frustum volume = pi depth (RR+Rr+rr)/3. Anyway, there must be lots of "nice" cubics out there that textbooks and puzzlists routinely shun. Suggestions? --rwg __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com