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2020-2021:teams:manespace:解析几何基础知识

解析几何基础和常用结论

三角形面积公式

已知三点坐标的面积公式：

由三点$(x1,y1),(x2,y2),(x3,y3)$组成的三角形面积为$S=\frac{1}{2}|x1y2-x1y3+x2y3-x2y1+x3y1-x3y2|$

一点为原点的三角形面积公式

二点(x1,y1),(x2,y2),面积为$S=\frac{1}{2}|{x1y2-x2y1}|$