The sum of the two vectors is the vector that begins at the origin of the first vector and goes to the ending of the second vector, as shown below. The resultant, or sum, vector would be the vector fr...The sum of the two vectors is the vector that begins at the origin of the first vector and goes to the ending of the second vector, as shown below. The resultant, or sum, vector would be the vector from the origin of the first vector to the arrowhead of the last vector; the magnitude and direction of this sum vector would then be measured.