PHI

The PHI function calculates the third angle (in radians) of a body-fixed-3-1-3 Euler rotation sequence between markers i and j. Marker j defaults to the global coordinate system if it is not specified. See Figure 1 for a schematic description of the body-fixed-3-1-3 Euler rotation sequence.

Format

PHI(i[,j])

Arguments

i	The marker whose rotations are being sought.
j	The marker with respect to which the rotations are being measured.

Examples

REQUEST/1, F2=PHI(222,434)

This REQUEST statement output the phi angle between Markers 222 and 434 in its second column.

Figure 1. Body-fixed-3-1-3 Euler Angles

	The body-fixed-3-1-3 sequence is started by rotating counterclockwise the initial system of axes, xyz, by an angle about the z-axis. The resultant axes are labeled . (Notice that z coincides with . )

	In the second stage the intermediate axes, , are rotated counterclockwise about the -axis by an angle . The new resultant planes are labelled ' ' '. The '- axis is at the intersection of the xy and ' ' planes and is known as the line of nodes. (Notice that coincides with '.)

	In the final rotation, the '- '- z '- axes are rotated counterclockwise by an angle f about the -axis to produce the x' y' z' axes, which is the desired final direction. (Notice that coincides with '.)

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