Study guide and 16 practice problems on:

Definition of vector length

The length of the 2d vector $\mathbf{x} = \langle x_1, x_2 \rangle$ is $|\mathbf{x}| = \sqrt{x_1^2 + x_2^2}$.
The length of the 3d vector $\mathbf{x} = \langle x_1, x_2, x_3 \rangle$ is $|\mathbf{x}| = \sqrt{x_1^2 + x_2^2 + x_3^2}$.