Cartesian coordinates in space

Take three mutually perpendicular lines x, y, z intersecting at point O. Let us draw planes through each pair of lines. We obtain three planes xy, xz and yz.
These straight lines x, y and z are called coordinate axes .
The xy, xz, and yz planes are called coordinate planes .
The point O - the point of intersection of the lines x, y and z is called the origin.



The x coordinate of the point A is a number equal to the absolute value of the length of the segment OAx: positive if the point Ax lies on the positive semi-axis x, negative if on the negative semi-axis.
The coordinates of point A in space are written as: A (x; y; z)