7.2. Operations with Vectors http://www.ck12.org
92 = 12. 662 + 52 − 2 · 12. 66 · 5 ·cosθ
θ= 34. 6 ◦Example C
Elaine started a dog walking business. She walks two dogs at a time named Elvis and Ruby. They each pull her in
different directions at a 45◦angle with different forces. Elvis pulls at a force of 25Nand Ruby pulls at a force of
49 N. How hard does Elaine need to pull so that she can stay balanced? Note: N stands for Newtons which is the
standard unit of force.
Solution: Even though the two vectors are centered at Elaine, the forces are added which means that you need to
use the tail-to-head rule to add the vectors together. Finding the angle between each component vector requires
logical use of supplement angles.