3-5 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} a&=9.5\\ b&=7.5\\ \phi_{ab}&=55\degree\\ \end{cases} $$ $$\ab{a}$$ $$ \begin{aligned} \vec a \cdot \vec b&=ab\cos\phi\\ &=(9.5)(7.5)\cos55\degree\\ &\approx 40.86732109001203\\ &\approx 41\\ \end{aligned} $$ $$\ab{b}$$ $$ \begin{aligned} \abs{\vec a \times \vec b}&=ab\sin\phi\\ &=(9.5)(7.5)\sin55\degree\\ &\approx 58.36458315559067\\ &\approx 58\\ \end{aligned} $$