Tangential Relations between Distorted Angles vs. Original Angles of a Traveling General Triangle in Special Relativity

Let's consider a traveling general triangle $\Delta $\textit{ABC,} with the speed $v$, along its side \textit{BC }on the direction on the $x-$axis; angles $B$ and $C$ are adjacent to the motion direction, while angle $A$ is of course opposite. Let \textit{AM} be the perpendicular from $A$ to the motion direction \textit{BC}. After the contraction of the side \textit{BC} with the Lorentz factor $C(v)=\sqrt {1-\frac{v^{2}}{c^{2}}} $, and consequently the contractions of the oblique-sides \textit{AB} and \textit{AC} with the oblique-contraction factor \[ OC(v,\theta )=\sqrt {C(v)^{2}\cos^{2}\theta +\sin^{2}\theta } , \] where $\theta $ is the angle between respectively each oblique-side and the motion direction, one gets the general triangle $\Delta A'B'C'$ with the following tangential relations between distorted angles vs. original angles of the general triangle: \[ \tan A'=\tan A\cdot C\left( v \right)\cdot \frac{1-\tan A_{1} \tan A_{2} }{1-\tan A_{1} \tan A_{2} C\left( v \right)^{2}}, \] where angles $A_{1} =BAM$and respectively $A_{2} =MAC$; \[ \tan B'=\frac{\tan B}{C\left( v \right)}; \] \[ \tan C'=\frac{\tan C}{C\left( v \right)}. \]