已知cos(π/6+a)=根号3/3求cos(5π/6-a)的值

问题描述:

已知cos(π/6+a)=根号3/3求cos(5π/6-a)的值

cos(π/6+a)=√3/3
cos(π-5π/6+a)=√3/3
cos[π-(5π/6-a)]=√3/3
-cos(5π/6-a)=√3/3
cos(5π/6-a)=-√3/3