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.

问题描述:

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