Question

If `A = <3 ,-1 ,-7 >`, `B = <5 ,8 ,-4 >` and `C=A-B`, what is the angle between A and C?

Answer 1

`x=arccos(24/sqrt5546)`

Explanation:

`C=<3-5,-1-8,-7-(-4)>=<-2,-9,-3>`

`cosx=(A*C)/(sqrt(3^2+(-1)^2+(-7)^2)*sqrt((-2)^2+(-9)^2+(-3)^2))`

`cosx=(3*(-2)+(-1)*(-9)+(-7)*(-3))/(sqrt(59)*sqrt(94))`

`cosx=24/sqrt5546`