Which of the following is/are correct? If ` vec a= hat i+ hat j` and ` vec b=2 hat i- hat k` then the point of intersection of the lines ` vec rx vec a= vec bx vec a` and ` vec ax vec b= vec ax vec b` is 3` vec i+ vec j-k` `( vec rdot hat i)( hat i x vec r)+( vec rdot hat j)( hat jx vec r)+( vec rdot hat k)( hat k x vec r)= vec0` If `| vec a|=3,| vec b|=5,| vec c|=7` and ` vec a+ vec b+ vec c= vec0` then the angle between ` vec aa n d vec b` is `pi/3` If the vectors ` vec a , vec b& vec c` from the sides `B C ,C A&A B` respectively of a triangle `A B C` , then ` vec ax vec b= vec bx vec cx vec a`