f ( x ) = log4 {log4( x )} then f ′( x )
f ( x ) = [log {log4( x )}] /log4
(log4) [ f ( x ) ] = log { logx/log4} = [ log{logx}] / [log{log4}]
[log{log4}] (log4) [ f ( x ) ] = log{logx} ... differentiating w.r.to x
[log{log4}] (log4) [ f ' ( x ) ] = 1/{logx} {1/x}
f ' ( x ) = 1/ [ (log{log4}) {log4} {x (logx) } ]