In a triangle ABC, with usual notations if $\dfrac{s-a}{11} = \dfrac{s-b}{12} = \dfrac{s-c}{13}$ and $\lambda \tan^2 \dfrac{A}{2} = 455$, then $\lambda =$

With usual notations, in $\triangle ABC$, if $2a^2 = b^2 + c^2$, then $\dfrac{\cos 3A}{\cos A} + 2 =$

With usual notations, in $\triangle ABC$, $(b - c)^2 \cos^2 \dfrac{A}{2} + (b + c)^2 \sin^2 \dfrac{A}{2} =$

Let $A = \begin{bmatrix} -5 & -3 \\ 2 & 1 \end{bmatrix}$. The Row transformation $R_1 \rightarrow R_1 + 3R_2$ will transform matrix A into