## Precalculus (6th Edition) Blitzer

The vectors $\mathbf{i}$ and $\mathbf{j}$ both have magnitudes of 1 and are called unit vectors. The direction of vector $\mathbf{i}$ is along the positive x -axis. The direction of vector $\mathbf{j}$ is along the positive y-axis.
For representing the position vectors on the cartesian axis x, y, and z, the three systems of vectors, $\mathbf{i}$, $\mathbf{j}$, and $\mathbf{k}$ are used. They are mutually perpendicular with each other and point along the x-axis, y-axis, and z-axis respectively, and have a magnitude of 1. They are called unit vectors.