Chapter 1 - Units, Physical Quantities, and Vectors - Problems - Discussion Questions - Page 27: Q1.19

See work.

The scalar product of a vector with itself is the square of the vector’s magnitude, according to equation 1.16. The angle between a vector and itself is zero. The vector/cross product of a vector with itself is zero, according to equation 1.20. The angle between a vector and itself is zero.