Unit 4, Day 5

Agenda

1. Number talk: True or False — whatever multiplying two arrows turns out to mean, $\vec{a}\cdot \vec{b}=\vec{b}\cdot \vec{a}$
2. Random groups: invent a multiplication for arrows — every candidate rule tested; which one can detect an angle?
3. Consolidate: The Dot Product — two formulas, one number, and a perpendicularity test that falls out free
4. Practise: Dot and Cross Product Practice — the dot half

Things to do before our next class

• Journal: the dot product of two arrows comes out to zero. What do you now know, and why is it worth knowing?