zài / píngmiàn / jǐhé / lǐ / wǒmen / tōngcháng / yòng / zhíjiǎo / zuò biāo xì / lái / miáoshù / diǎn / de / wèizhì在平面几何里,我们通常用直角坐标系来描述点的位置。In plane geometry, we usually use a Cartesian coordinate system to describe the position of points.