File:Labels used for a triangle- of- velocities..JPG

According to trigonometry, if two sides of a triangle are known, then the third side can always be calculated. The triangle of velocities is used for the leg between take- off and approach. Its labels are defined as follows: CB is the mean wind forecast for the pressure surface p, period t, and ground position B(x,y); AC is the aircraft Heading and True Air Speed; AB is the aircraft ground speed and track; position A(xo,yo) is the departure; B is the DR ground position; C is the air position; and  is the wind-drift correction for the aircraft flight. (Courtesy of Soroti Flying School, Uganda).