(1)∵sina/2+cosa/2=2√3/3
∴平方得,1+sina=4/3
∴sina=1/3
∵a∈(π/2,π)
∴cosa=-√(1-sin²a)=-2√3/3
(2)∵a∈(π/2,π) b∈(0,π/2)
∴a+b∈(π/2,3π/2)
∵sin(a+b)=-3/5
∴a+b∈(π,3π/2) ,cos(a+b)=-4/5
∴sinb=sin(a+b-a)=sin(a+b)cosa-cos(a+b)sina=-3/5*(-2√3/3)-(-4/5)*1/3=2√3/5+4/15
(1)∵sina/2+cosa/2=2√3/3
∴平方得,1+sina=4/3
∴sina=1/3
∵a∈(π/2,π)
∴cosa=-√(1-sin²a)=-2√3/3
(2)∵a∈(π/2,π) b∈(0,π/2)
∴a+b∈(π/2,3π/2)
∵sin(a+b)=-3/5
∴a+b∈(π,3π/2) ,cos(a+b)=-4/5
∴sinb=sin(a+b-a)=sin(a+b)cosa-cos(a+b)sina=-3/5*(-2√3/3)-(-4/5)*1/3=2√3/5+4/15