Question 106431
Yes, 30 m is the magnitude of the position change vector (AB) but the direction is (3,-4) in (i,j) coordinates. 
You start at A (2,1) and go to B (2+i component of AB,1+j component of AB).
Find the magnitudes of the i component and the j component using the angle with vertex at A. 
{{{drawing( 300, 300, -10, 30, -30, 10,grid( 1 ),green(circle( 2, 1, .5 )),green(circle( 20, -23, .5 )),red(line(2,1,20,-23)),locate(2.5,4,A),locate(21,-23,B),blue(line(2,1,20,1)),blue(line(20,1,20,-23)))}}}
Hint : 3,4,5 make up a Pythagorean triple.
Sine and cosine of an angle using these sides are either 3/5 or 4/5.