Respuesta :

You should try an online calculator called tiger algebra...it really good and can answer question like these ones
HomertheGenius
f ( x ) = tan ( 2 x );
f ` ( x ) = (1 / cos² x )· ( 2 x )` = 2 / cos² x
f` ( π/6 ) = 2 / cos² (π/6) = 2 / (√3/2)² = 2 : 3/4 =  8/3