1 sentence

1. 在极坐标系中，极点通常用字母O来表示。

   zài jí​zuò​biāo​xì zhōng, jí​diǎn tōng​cháng yòng zì​mǔO lái biǎo​shì.

   In a polar coordinate system, the pole is usually represented by the letter O.

   Source: Dong Chinese Dictionary