X and Y coordinates of point on XY plane are Zero
We saw that to uniquely determine the position of a point in space, we use three mutually perpendicular axes, x, y and z. When we mark/plot these axes with a given origin, they divide the three dimensional plane into 8 octants. We discussed these in the video.
In this process, using the help of x and y coordinate we get a plane. We call it XY plane, which is marked in the above diagram. As you can see, any point on this plane will have z-coordinate equal to zero.(z-coordinate of a point will be +− perpendicular distance from XY plane, for a point on XY plane, perpendicular distance from XY plane will be zero). Same thing is applicable for XZ and YZ planes.
So, the given statement which says X and Y coordinate of a point on XY plane is zero is wrong. Only Z coordinate is always zero for a point on XY plane.