Question

If →A=5ˆi+7ˆj−3ˆk and →B=2ˆi+2ˆj+8ˆk the angle between →A and →B is

Answer 1

cos(thetta) = u.v/(|u|.|v|)

so we find , u.v= 10+14-24= 0

then zero divided by anything is equal to the 0.

cos(thetta)= 0

thetta = (cos)—1 (0)

thetta = 90°