数学2：已知sin(x+TT/12)=1/3,则cos(x+7TT/12)的值为（ ）.求详解,要步骤.谢谢.

数学2：已知sin(x+TT/12)=1/3,则cos(x+7TT/12)的值为（ ）.求详解,要步骤.谢谢.
数学2：已知sin(x+TT/12)=1/3,则cos(x+7TT/12)的值为（ ）.求详解,要步骤.谢谢.

数学2：已知sin(x+TT/12)=1/3,则cos(x+7TT/12)的值为（ ）.求详解,要步骤.谢谢.
cos(x+7π/12)
=cos(x+π/12+π/2)
=-sin(x+π/12)
=-1/3