Vectors

(a1, a2, a3) = a1i + a2j + a3k   (basis i, j, k)
(a1,a2,a3) . (b1,b2,b3) = a1b1 + a2b2 + a3b3   ("dot product",
  & other dimensions)
(a1,a2,a3) × (b1,b2,b3) = (a2b3-a3b2, a3b1-a1b3, a1b2-a2b1)   (3D "cross product")
  =
| ijk |
| a1a2a3 |
| b1b2b3 |
  (as a determinant)