into the geometry of deformations equation:

${\mathrm{\varphi }}_{\mathrm{C}}={\mathrm{\varphi }}_1+{\mathrm{\varphi }}_2$

to derive an equation for the rotation angle at $\mathrm{C}$:

${\mathrm{\varphi }}_{\mathrm{C}}=\frac{{\mathrm{T}}_1{\mathrm{L}}_1}{{\mathrm{J}}_1{\mathrm{G}}_1}+\frac{{\mathrm{T}}_2{\mathrm{L}}_2}{{\mathrm{J}}_2{\mathrm{G}}_2}$