INDEX finger coordination

Figure 3.2 depicts the three-dimensional version of Cartesian coordinates. We define the x and y axes as before, and erect the z axis through the origin and perpendicular to the X and y axes. We will use a right-handed coordinate system like that of Figure 3.1. For this case, if the thumb of the right hand points in the direction of the positive x axis and the index finger points in the direction of the positive y axis, the middle finger can point in the direction of the positive z axis. If the left hand must be used for such an alignment, the coordinate system is called a left-handed coordinate system.

CONVENTION. A right-handed coordinate system is chosen Le. a, b and c are taken in the order of the thumb, index and middle finger of the right hand a is the angle between b and c, p is the angle between a and c, y is the angle between... 

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