Triangle Rule for Vector Addition
If $\mathbf{v}$ and $\mathbf{w}$ are vectors in 2 -space or 3 -space that are positioned so the initial point of $\mathbf{w}$ is at the terminal point of $\mathbf{v}$, then the $\boldsymbol{s u m} \mathbf{v}+\mathbf{w}$ is represented by the arrow from the initial point of $\mathbf{v}$ to the terminal point of $\mathbf{w}$