Question

The points A and B have position vectors a  and vector b  relative to an origin O, where vector a = 4i + 3j + 2k and vector b = 7i + 5j + 4k

(i) Find the length of AB. 

(ii) Use a scalar product to find angle OAB.

Answer 1

(i) Find vector (a - b)  or vector (b - a) irrespective of label (expect 11i - 2j - 6k or −11i + 2j + 6k) Magnitude of vector = √161 

(ii) Using vector (AO or OA) and vector (AB or BA)