3-29 할리데이 11판 솔루션 일반물리학

$$\begin{cases} a&=4.30\\ b&=6.20\\ \phi&=50.0\degree\\ \end{cases}$$ $$\ab{a}$$ $$\begin{aligned} A&=\frac{1}{2}ab\sin\phi\\ &=\frac{1}{2}\cdot4.3\cdot6.2\sin50\degree\\ &\approx 10.21137242677598\\ &\approx 10.2\\ \end{aligned}$$ $$\ab{b}$$ $$\vec a\times \vec b =ab\sin\phi,$$ $$\begin{aligned} A&=\frac{1}{2}ab\sin\phi\\ &=\frac{1}{2}\(\vec a\times \vec b\)\\ \end{aligned}$$