设\(x_{1}\)，\(x_{2}∈(0, \dfrac {π}{2})\)，且\(x_{1}\neq x_{2}\)，下列不等式中成立的是\((\)　　\()\)
\(① \dfrac {1}{2}(\sin x_{1}+\sin x_{2}) > \sin \dfrac {x_{1}+x_{2}}{2}\)；
\(② \dfrac {1}{2}(\cos x_{1}+\cos x_{2}) > \cos \dfrac {x_{1}+x_{2}}{2}\)；
\(③ \dfrac {1}{2}(\tan x_{1}+\tan x_{2}) > \tan \dfrac {x_{1}+x_{2}}{2}\)；
\(④ \dfrac {1}{2}( \dfrac {1}{\tan x_{1}}+ \dfrac {1}{\tan x_{2}}) > \dfrac {1}{\tan \dfrac {x_{1}+x_{2}}{2}}\)．