Beginning at the origin O, draw a vector equal and opposite to OA and label its head C (fig. 8). Vector OC represents the effect required to balance (reduce the unbalance to zero). For simplification, vector AB is shifted to the origin O and shown as OB'. An effect equal to OC is needed to balance the unit. To make OB' equal to OC, OB' must be rotated 42º to the same angular position as OC and increased by the ratio OC/OB'.