R=P+Q is a vector representatiion.
This should be written as
vecR=vecP+vecQ→R=→P+→Q which means sum of two vectors.
Here R=abs(vecR)="Length of the diagonal of the "R=∣∣∣→R∣∣∣=Length of the diagonal of the "parallelogram"parallelogram P= abs(vecP)= "Length of one side of the "P=∣∣∣→P∣∣∣=Length of one side of the "parallelogram"parallelogram
Q=abs(vecQ)="Length of another adajacent side" Q=∣∣∣→Q∣∣∣=Length of another adajacent side "of the parallelogram"of the parallelogram