Vector Sum (벡터의 합)

Prallelogram Rule for Vector Addition
If @@\textbf{u}@@ and @@\textbf{v}@@ are vector in 2-space of 3-space that are positioned so their initial points coincide,
then the two vectors form adjacent sides of a parallelogram, and the sum @@\textbf{u}+\textbf{v}@@ is the vector represented
by the arrow from the common initial point of @@ \textbf{u}@@ and @@\textbf{v}@@ to the opposite vertex of the parallelogram.