The figure shows a shape $$ABC$$ and its minor image $${A_1}$$$${B_1}$$$${C_1}$$ across the horizontal axis ($$x$$-axis). The coordinate transformation matrix that maps $$ABC$$ to $${A_1}$$$${B_1}$$$${C_1}$$ is

The eigen values of the matrix $$A = \left[ {\matrix{ 1 & { - 1} & 5 \cr 0 & 5 & 6 \cr 0 & { - 6} & 5 \cr } } \right]$$ are

If $$V$$ is a non-zero vector of dimension $$3 \times 1,$$ then the matrix $$\,A = V{V^T}$$ has a rank $$=$$ ________

The angle between two vectors $${X_1} = {\left[ {\matrix{ 2 & 6 & {14} \cr } } \right]^T}$$ and $${X_2} = {\left[ {\matrix{ { - 12} & 8 & {16} \cr } } \right]^T}$$ in radian is ________.