How do you find the angle, θ, between the vectors? If needed, round your answer to the nearest tenth.


1.) u = 2i - 3j
v = i - 2j

2.) u = <3, 2>
v = <4, 0>

1 answer

1.
dot product
u ∙ v = |u| |v| cosØ, where Ø is the angle between them, so
<2,-3> ∙ <1,-2> = √13 √5 cosØ
2+6 = √13√5cosØ
cosØ = 8/(√13√5) = .99227...
Ø = appr 7.1°

do #2 the same way