## Calculus: Early Transcendentals (2nd Edition)

$\textbf{u}\cdot\textbf{v} = 0$
$\textbf{u}\cdot\textbf{v} = u_1v_1 + u_2v_2$, where $\textbf{u} =$ and $\textbf{v} =$. $\textbf{u}\cdot\textbf{v} = (1)(1) + (1)(-1) = 1 - 1 = 0$