find the angles between the vectors...?

[screwaround]

cosx |U|*|V| = dot product U*V
cosx *?5 * ?10 = -6+1=-5
cosx=-5/?50
x=135 degrees

 

[roni10]

U=<2,1> and V=<-3,1>
please please anyone help me! i dont know how to find the angles!

 

[michaelempeigne]

cos x = - 5 / [ sqrt 5 * sqrt 10 ]
cos x = - sqrt 2 / 2
x = 135 degrees