已知cos(a-β/2)=-1/9,sin(a/2-β)=2/3且π/2

Question

已知cos(a-β/2)=-1/9,sin(a/2-β)=2/3且π/2

Answer 1

sin(a-β/2)=±√{1 - [cos(a-β/2)]^2} =±(4√5)/9
∵0