已知cos(π/6 –α)=√3/3,则cos(5π/6 +α)的值是多少? 要具体步骤
问题描述：
已知cos(π/6 –α)=√3/3,则cos(5π/6 +α)的值是多少? 要具体步骤
答
cos(-π/6 +α)=√3/3
cos(-π/6 +α+π)=cos(5π/6 +α)=-√3/3