Multi dot product

[fizali]

ı need to learn how can ı calculate ' del . r (A . r) ' where 'A' is a constant vector , 'r' is a distance vector and '.' is dot product. the result must be 4(a.r)

 

[fizali]

vector operator dot

how can ı find the solution of the this equation. ' del . r (r.A)= 4(r.A) '