Chapter 7 - Applications of Trigonometry and Vectors - Section 7.5 - Applications of Vectors - 7.5 Exercises - Page 343: 46

$\langle 0,-4 \rangle$= 0 $ \textbf i $-4 $ \textbf j$

$\langle 0,-4 \rangle$= $\langle 1\times 0,0 \rangle$+ $\langle 0,-4 \rangle$ $\langle 0,-4 \rangle$= 0 $\langle 1,0 \rangle$-4 $\langle 0,1 \rangle$ $\langle 0,-4 \rangle$= 0 $ \textbf i $-4 $ \textbf j$