document.write( "Question 814556: ABCD is a quadrilateral. Find the sum of vectors BA , BC , CD DA \n" ); document.write( "
Algebra.Com's Answer #490398 by jsmallt9(3758)\"\" \"About 
You can put this solution on YOUR website!
  1. Draw four points in the shape of some quadrilateral.
  2. Label the four points A, B, C and D.
    1. Any point can be A.
    2. Then go clockwise (or counterclockwise) to the next point and label it B.
    3. Continue on the same direction to the next point and label it C.
    4. Label the last point D
  3. Draw the last three vectors: BC, CD and DA. (Remember, the first letter is where the arrow starts and the second letter is where the arrowhead is.)
  4. If you look at these last three vectors and if you understand vector addition, you will see that the sum of these three vectors is BA!
  5. So BA + (BC+CD+DA) = BA + BA = 2BA
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