"I am thinking therefore I exist." (Latin:Cogito ergo sum) from the Discourse on Method Coordinate System: （坐标系) Cartesian coordinate system(直角坐标系) polar system(极坐标系) Coordinate System：（坐标系） Cartesian coordinate system（直角坐标系） polar system（极坐标系） "I am thinking therefore I exist." (Latin: Cogito ergo sum) from the Discourse on Method