Chapter 7 - Applications of Trigonometry and Vectors - Section 7.5 Applications of Vectors - 7.5 Exercises - Page 342: 21

$\langle a,b\rangle=\langle -3.0642,2.5712\rangle $

$u=\langle a,b\rangle=\langle |u|\cos\theta,|u|\sin\theta\rangle$ Substitute $|u|=4$ and $\theta=140^\circ$: $\langle a,b\rangle=\langle4\cos 140^\circ,4\sin140^\circ\rangle $ $\langle a,b\rangle =\langle-3.0642,2.5712 \rangle$