$σ_{t} = σ_{1} - σ_{2} 2 \sin 2 \theta - τ \cos 2 \theta$

$σ_{t} = σ_{1} + σ_{2} 2 \sin 2 \theta + τ \cos 2 \theta$

$σ_{t} = σ_{1} - σ_{2} 2 \sin 2 \theta + τ \cos 2 \theta$

$σ_{t} = σ_{1} + σ_{2} 2 \sin 2 \theta - τ \cos 2 \theta$