What is the angle between vectors a = (1,2) and b = (1,− 1/ 2 ) .

Question

What is the angle between vectors a = (1,2) and b = (1,− 1/2 ) .

Answer 1

If you take the dot (scalar) product:

a•b = 1·1 + 2·(-1/2) = 1 - 1 = 0

Since the dot product is zero, the vectors are perpendicular to one another.