Stresses acting on an infinitesimal soil element are shown in the figure (with σz > σx). The major and minor principal stresses are σ1 and σ2, respectively. Considering the compressive stresses as positive, which one of the following expressions correctly represents the angle between the major principal stress plane and the horizontal plane?
1
\(\rm \tan^{-1} \left( \frac{\tau_{zx}}{\sigma_1 - \sigma_x} \right)\)
2
\(\rm \tan^{-1} \left( \frac{\tau_{zx}}{\sigma_3 - \sigma_x} \right)\)
3
\(\rm \tan^{-1} \left( \frac{\tau_{zx}}{\sigma_1 + \sigma_x} \right)\)
4
\(\rm \tan^{-1} \left( \frac{\tau_{zx}}{\sigma_1 + \sigma_3} \right)\)