If A = <8 ,3 ,2 >, B = <-1 ,-1 ,5 >, and C=A-B, what is the angle between A and C?

$C = < 8 - \left(- 1\right) , 3 - \left(- 1\right) , 2 - 5 > = < 9 , 4 , - 3 > \to \cos \theta = \frac{A \cdot C}{| A | | C |} = \frac{< 8 , 3 , 2 > \cdot < 9 , 4 , - 3 >}{\sqrt{{8}^{2} + {3}^{2} + {2}^{2}} \sqrt{{9}^{2} + {4}^{2} + {\left(- 3\right)}^{2}}}$ $\theta = {\cos}^{-} 1 \left(\frac{\left(8\right) \left(9\right) + \left(3\right) \left(4\right) + \left(2\right) \left(- 3\right)}{\sqrt{77} \sqrt{106}}\right) = {\cos}^{-} 1 \left(\frac{78}{\sqrt{8162}}\right) , \theta = {30.3}^{\circ}$