Question

If `A = <2 ,6 ,-8 >`, `B = <-9 ,4 ,-2 >` and `C=A-B`, what is the angle between A and C?

Answer 1

`50.67^o`

Explanation:

C would be <11,2,-6>

Now if the angle between A and C is `theta`, then `cos theta =(A.C)/(|A| |C|)`

`=(11*2 + 2*6 + (-8)*(-6))/(sqrt(2^2 +6^2 +(-8)^2) sqrt(11^2 +2^2 +(-6)^2)`

`=(22+12+48)/(sqrt 104 sqrt 161)`

`=82/sqrt16744`

`=82/129.399`

`=0.634`

`theta =50.67^o`