Problem:Express the vector PQ in standard form and find its length where: 
> P := [5,7]: Q := [6,8]:

The coordinates of the vector PQ are given by the coordinates of QP. Hence, 
> PQ := evalm(QP);
PQ := [1, 1]
Its lenth is given by the square root of the sum of the squares of the entries. 
> len := v > sqrt(dotprod(v,v)):
> lenth_of_PQ := len(PQ);
1/2 lenth_of_PQ := 2