Question

Evaluate the dot product a⃗ ⋅b⃗ of a⃗ =3i^−8j^ and b⃗ =−2i^−6j^.

Answer 1

The "dot product" of two vectors has several different formulas.

Since you are given the x- and y-coordinates of both vectors a and b, we can apply the formula

a dot b  = ax*bx + ay*by, where ax=x-component of vector a, by=y comp of vector b, and so on.  

So, for the problem at hand, ax * bx + ay * by becomes

3(-2) + (-8)(-6) = -6 + 48 = 42 (answer).  Note that the dot product (or "scalar product" is itself a scalar.