由题意知：cosx=1/7 cos(x-y)=13/14则通过计算可得：sinx=4√3/7 sin(x-y)=3√3/14用余弦公式:cosx·cos(x-y)+sinx·sin(x-y)=cos[x-(x-y)]=cosy即cosy=(1/7·13/14)+(4√3/7·3√3/14)=1/2cosy=0.5 y=π/3...