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MATHEMATICS FOR AIR CREW TRAINEES 46

the wind velocity vector originates at the same point as the course line. Wind velocity, 15 mph, is represented by a line 1.5 cm long from the direction 230°. Since air speed, 110 mph, is known but heading is not, the compass is set with a radius of 11 cm (11 cm = 100 mph), and, using the head of the wind velocity vector as center, strike an are which will intersect the course line. The line drawn from this point to the head of the wind vector has the length and direction of the air speed heading vector. The segment of the course line cut off by the intersecting arc is the length representing the ground speed. The parallelogram is completed in such a way that all three vectors originate from the origin point with the wind velocity vector and the air speed heading vector as sides and the ground speed track vector as the diagonal. 

c. The solution of the same problem by the triangle method is given next.

(1) Draw the north line.

[[image: drawing of a triangle of airspeed, ground speed and wing speed. The North Line is also shown]]
Figure 58.


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