The deaf people have their own ways _______ with each other.
A:talk
B:talking
C:to talk
D:for talking
在△ABC中,角A,B,C所对的边分别为a,b,c,若向量 m→ =(﹣cosB,sinC), n→ =(﹣cosC,﹣sinB),且 m→⋅n→=12 .
(Ⅰ)求角A的大小;
(Ⅱ)若b+c=4,△ABC的面积 S=3 ,求a的值.
选修4-5:不等式选讲
已知函数f(x)=|2x﹣a|+a.