3-40 할리데이 11판 솔루션 일반물리학

$$\begin{cases} \text{East}:+\i\\ \text{North}:+\j\\ \text{up}:+\k\\ \end{cases}$$ $$\ab{a}$$ $$\begin{aligned} \Ans&=\(-\j\)\times\(-\i\)\\ &=(-1)(-1)\(\j\times\i\)\\ &=\(\j\times\i\)\\ &=(-1)\(\i\times\j\)\\ &=(-1)\(\k\)\\ &=-\k\\ &\text{Down} \end{aligned}$$ $$\ab{b}$$ $$\begin{aligned} \Ans&=\(-\k\)\times\(-\j\)\\ &=(-1)(-1)\(\k\times\j\)\\ &=\(\k\times\j\)\\ &=(-1)\(\j\times\k\)\\ &=(-1)\(\i\)\\ &=-\i\\ &\text{West} \end{aligned}$$ $$\ab{c}$$ $$\begin{aligned} \Ans&=\i\times\k\\ &=(-1)\(\k\times\i\)\\ &=(-1)\(\j\)\\ &=-\j\\ &\text{South} \end{aligned}$$ $$\ab{d}$$ $$\begin{aligned} \Ans&=\i\cdot\i\\ &=1\cdot1\cdot\cos0\\ &=1 \end{aligned}$$ $$\ab{e}$$ $$\begin{aligned} \Ans&=\(\j\)\times\(\j\)\\ &=1\cdot1\cdot\sin0\\ &=0 \end{aligned}$$