3-8 할리데이 10판 솔루션 일반물리학

$$\begin{cases} \vec a:(0,2.5)\\ \vec b:(-3.0,0)\\ \vec c:(0,-4.2)\\ \end{cases}$$
(a)

$$\vec x = \vec a+\vec b+\vec c = (-3.0,-1.7)$$
(b)$\abs{\vec x}=?$ $$\begin{aligned} \abs{\vec x} &= \sqrt{(-3.0)^2+(-1.7)^2}\\ &=\frac{\sqrt{1189}}{10}\ut{m}\\ &\approx 3.5\ut{m}\\ \end{aligned}$$
(c)$\theta_x=?$ $$\begin{aligned} \theta_x&=\tan^{-1}\(\frac{-1.7}{-3.0}\)\\ &\approx -2.6\ut{rad} \end{aligned}$$