#2015_13 I just started learning calculus

Calculus Level 3

$\large { (\tan { x } ) }^{ { (\tan { x }) }^{ { (\tan { x }) }^{ { . }^{ .{ }^{ . } } } } }$

Find the value of derivative of the function above at $x=\frac { \pi }{ 4 }$ .