已知sin(a- (4/π))=1/3,则cos((π/4)+a)的值等于什麼

已知sin(a- (4/π))=1/3,则cos((π/4)+a)的值等于什麼
已知sin(a- (4/π))=1/3,则cos((π/4)+a)的值等于什麼

已知sin(a- (4/π))=1/3,则cos((π/4)+a)的值等于什麼
我觉得lz应该是打错题了
应该是sin(a-(π/4))=1/3
cos(a+π/4）=cos(a-π/4+π/2)=-sin(a-π/4)=-(1/3)