the unit disc的用法和樣例：
例句
- In this question, all unnamed circles are unit circles.
在本題內，所以不命名的圓皆為單位圓。 - Classical complex variable method is followed, but a new conformal mapping formula is proposed so that the exterior part of the parabolic crack is mapped into a unit circle.
採用了傳統的複變函數保角映射法，給出了一個新的保角變換公式，從而將拋物線曲裂紋外的區域映射到一個複平面的單位圓內。
