REDWOOD CITY, Calif. – Dust off the slide rules and recharge the calculators. Square Root Day is upon us. The math-buffs' holiday, which only occurs nine times each century, falls on Tuesday — 3/3/09 (for the mathematically challenged, three is the square root of nine). "These days are like calendar comets, you wait and wait and wait for them, then they brighten up your day — and poof — they're gone," said Ron Gordon, a Redwood City teacher who started a contest meant to get people excited about the event. The winner gets, of course, $339 for having the biggest...