Bivectors
- a^b is a bivector (2-blade)
- a^b directed area element in plane spanned by a and b
- a and b parallel then a^b=0 (parallel test)
- Same plane, same area: same bivector
- e1^e2 == e1^(e1+e2)
- "Reshapable"
- Bivectors form a linear space
- Claim: Bivectors are better characterization of tangent plane than normal vector