Notes
vector

Vector

A vector describes the relative displacement from one point in the plane to another. It is written in the form (3 5)\begin{pmatrix} 3 \\ 5 \end{pmatrix} where the first (top) component represents the horizontal displacement (parallel to the xx-axis) and the second represents the vertical displacement (parallel to the yy-axis). Positive numbers represent displacement in the positive direction, negative in the opposite.

Vectors can be added, subtracted, and scaled by applying these operations component by component:

(3 4)+(2 7) =(1 11) (3 4)(2 7) =(5 3) 3(2 7) =(6 21) \begin{aligned} \begin{pmatrix} 3 \\ 4 \end{pmatrix} + \begin{pmatrix} -2 \\ 7 \end{pmatrix} &= \begin{pmatrix} 1 \\ 11 \end{pmatrix} \\ \begin{pmatrix} 3 \\ 4 \end{pmatrix} - \begin{pmatrix} -2 \\ 7 \end{pmatrix} &= \begin{pmatrix} 5 \\ -3 \end{pmatrix} \\ 3\begin{pmatrix} -2 \\ 7 \end{pmatrix} &= \begin{pmatrix} -6 \\ 21 \end{pmatrix} \end{aligned}

Two vectors are parallel if one is a scale multiple of the other.