End of this Lengthy Chapter

Here are some terms and formulae you may wish to review at length:

• Length of a 2D vector parallel with a coordinate axis.
• Pythagorean Formula.
• Formula for 2D vector length (first version.)
• Formula for 2D vector length (second version.)
• The triangle inequality.
• Formula for 3D vector length.
• Length is always positive or zero.
• Length of the negative of a vector.