终边相同角差 360° 的整数倍；扇形弧长 l=∣α∣R。
In the casino game called roulette, a common bet is to place a bet on red or black. If the ball lands on the chosen c…
十个筹码上场，赢到一百个就走。赌局略不利——每局赢面不到二分之一。
