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 ________.

Let $$\,\,f:\left[ { - 1, - } \right] \to R,\,\,$$ where $$\,f\left( x \right) = 2{x^3} - {x^4} - 10.$$ The minimum value of $$f(x)$$ is _______.

The maximum value of $$f\left( x \right) = {x^3} - 9{x^2} + 24x + 5$$ in the interval $$\left[ {1,6} \right]$$ is

Consider the function $$\,\,y = {x^2} - 6x + 9.\,\,\,$$ The maximum value of $$y$$ obtained when $$x$$ varies over the interval $$2$$ to $$5$$ is