u•v = (-3)(1) + (-4)(-2) = 5
also, recall that
u•v = |u| |v| cosθ
so, now you have
5*√5 cosθ = 5
cosθ = 1/√5
θ = 63.43°
Find cosθ between two vectors v = (-3, -4) and u = (1, -2).
(A)√5/4 (B) 3/√2 (C) √5/5 (D) 0.8
1 answer