# If A = <4 ,3 ,-7 >, B = <5 ,8 ,-3 > and C=A-B, what is the angle between A and C?

C = ( $-$1, $-$5, $-$4 )
= arc cos { (xu + yv + zw ) / (sqrt ( x^2 + y^2 + z^2 )sqrt( u^2 + v^2 + w^2))}
Here, the angle is arc cos ( 9 / sqrt3108)