TABLE OF CONTENTS Let X ?OX, Y ?OY and Z ?OZ be three mutually perpendicular straight lines in space, intersecting at O. Then the point O is called the origin. The three lines X ?OX, Y ?OY and Z ?OZ are respectively called the x-axis, the y-axis and the z-axis. The three lines taken together are called the rectangular coordinate axes or simply the coordinate axes. The positive directions of these axes are indicated by the arrow heads.
The three axes, taken two at a time, determine three coordinate planes. The plane XOY, determined by the x-axis and the y-axis, is called the XY-plane. Similarly, the plane YOZ is called the YZ-plane and the plane ZOX is called the ZX-plane. These three planes, taken together, are called the rectangular coordinate planes or simply the coordinate planes. The coordinate planes divide the entire space into 8 parts called the octants. The octant determined by the positive directions of the coordinate axes, i.e., the octant XOYZ is called the positive or the first octant.
Note. The system of coordinate axes is called right-handed when OX, OY and OZ are oriented counter-clockwise. Throughout the book, we shall use the right-handed system of coordinate axes.
