If A = <3 -1 3 > B = <2 -3 5 > and C=A-B what is the angle between A and C?

##112.47^0##
C= A-B= <3-13>– <2 -3 5> = < 12-2>
Angle between A and C would be given by ##cos theta=(A*C)/(|A| |C|)##
##cos theta = (3*1 +(-1)*2 + 3(-2))/ (sqrt(3^2 +(-1)^2 +3^2) sqrt(1^2+2^2 +(-2)^2))##
=##-5/(sqrt19 sqrt9)##= -0.3823
##theta= arccos-0.3823## =##112.47^0##