Triangle law of vector addition: According to this law, if two vectors are represented by two sides of a triangle taken in order, then their vector total is represented by third side of triangle taken in the opposite order.

Two vectors A and B of Figure 3(a) can be added geometrically by first drawing A on a piece of graph paper to a given scale so that its direction is specified to a coordinate system. Then draw vector B to the same scale with the tail of B starting at the tip of A, as shown in Figure 3(b).

The resultant R = A + B is the vector drawn from the tail of A to the tip of B. This procedure is called Triangle method of vector addition.

The resultant does not change if B is taken first and then the tail of A starts at the tip of B and the resultant runs from the tail of B to the tip of A, as in Figure 3(c).