find the angle between these lines

Question

[x,y,z] = [3,4,1] + s[-1,5,-2]
[x,y,z] = [8,5,-9] + t[2,3,-6]

Answer 1

recall that you can find the angle θ between vectors u and v using

u•v = |u|*|v|*cosθ

so, just plug and chug:

-2+15+12 = √30√49*cosθ
cosθ = 25/(7√30) = .652
θ = 0.86 = 49.3°

Answer 2

thank you !!