Explain why the point with polar coordinates $(0,0)$ is an intersection point of the curves $r=cos$ and $r=sin$ even though $cossin$ when $=0.$

As $$ increases from $0$ to $2,cos$ is generated counterclockwise, beginning at $$ The function $cos$ passes through $0$ when $=q,$ As $$ increases fro $=0$ and $2.$ There is no foolproof rule for detecting such "hidden" intersection points. Care must be used.