Easy Practice — Set 2

Quick Recap — Dot & Cross Products

• $\vec a\cdot\vec b=|\vec a||\vec b|\cos\theta$ (a scalar); $|\vec a\times\vec b|=|\vec a||\vec b|\sin\theta$ (a vector).
• $\vec a\cdot\vec b=0\Rightarrow$ perpendicular; $\vec a\times\vec b=\vec0\Rightarrow$ parallel.
• Area: parallelogram $=|\vec a\times\vec b|$; triangle $=\tfrac12|\vec a\times\vec b|$.
• Scalar triple product $[\vec a\,\vec b\,\vec c]=\vec a\cdot(\vec b\times\vec c)$; zero $\Rightarrow$ coplanar.