(Ⅰ) ;
(Ⅱ) cos2( +α)﹣sin(π﹣α)cos(π+α)+2.
(Ⅰ)求f(x)的解析式;
(Ⅱ)已知f( + )= ,﹣ <a<0,求cos(a﹣ )的值.
(Ⅱ)当 ,求f(x)的值域.