The Oz axis points to the mass center of the Earth E, the Ox axis is normal to the Oz axis in the orbital plane and points along the direction of an increasing

polar angle [alpha], and the coordinate system is right-hand oriented.

The distribution function of the

polar angle [theta] is

The temperature is sought in the form of a product of two functions, one of which depends on the variable r, and the other depends only on the

polar angle [theta].

For the polar ([theta]) and azimuthal ([phi]) angles, the azimuthal angle, [phi], earns the values from 0 to 2[pi], while the

polar angle, ([theta]), earns four different values built on the source-to-detector configuration.

This is done for the i different orientations of the

polar angle [theta].

Caption: Figure 2: Radial displacement ([u.sup.*.sub.r]) versus

polar angle at r = b for different wave numbers ([k.sup.(2).sub.2]b) for a tunnel in hard soil.

[theta] is the

polar angle. C is the amplitude of a harmonic component.

where [r.sub.p] is polar radius of pole O in a polar coordinate system; [[theta].sub.p] is

polar angle of pole O in a polar coordinate system; [[sigma].sub.r] is normal stress on a microelement of the rock along the polar radius; [[sigma].sub.[theta]] is normal stress on a microelement of the rock along the

polar angle; and [[tau].sub.r[theta]] is shear stress on a microelement of the rock along the polar radius/angle.

If the interaction is within the layer, the particle's direction is updated by sampling the Henyey-Greenstein distribution for the

polar angle [theta] relative to the direction of travel.

The cam rotation angle, [fi], must be differentiated from the

polar angle [beta] that determines the position vector of point B with respect the oxy coordinate system.

We consider an infinitesimal mass dM of the sphere represented by its spherical coordinates (r, [theta], [phi]), where r is the radial distance, [theta] the

polar angle, and [phi] the azimuthal angle (see Figure 4).