color(red)((1-tan^2 x))tan 2x=2sqrt3 ?
tan (a+b)=(tan a+tan b)/(1-tan a*tan b)
tan (x+x)=tan(2x)=(tan x+tan x)/(1-tan x*tan x)
tan 2x=(2tan x)/(1-tan^2 x)
color(red)(1-tan^2 x)=(2 tan x)/(tan 2x)
"let us write the equation again"
((2 tan x)/cancel((tan 2x)))cancel(tan 2x)=2sqrt3
"yields :"
cancel(2) tan x=cancel(2) sqrt 3
tan x=sqrt3