已知cos(a-B/2)=-1/9,sin(a/2-B)=2/3,且π/2
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![已知cos(a-B/2)=-1/9,sin(a/2-B)=2/3,且π/2](/uploads/image/z/1786681-1-1.jpg?t=%E5%B7%B2%E7%9F%A5cos%28a-B%2F2%29%3D-1%2F9%2Csin%28a%2F2-B%29%3D2%2F3%2C%E4%B8%94%CF%80%2F2)
已知cos(a-B/2)=-1/9,sin(a/2-B)=2/3,且π/2
已知cos(a-B/2)=-1/9,sin(a/2-B)=2/3,且π/2
已知cos(a-B/2)=-1/9,sin(a/2-B)=2/3,且π/2
∵π/2
π/4
cos[(a-B/2)-(a/2-B)]=cos[(a+b)/2]=cos(a-B/2)cos(a/2-B)+sin(a-B/2)sins(a/2-B)=-1/9 * √5/3+
4√5/9 * 2/3=7√5/27
cos(a+B)=2cos[(a+b)/2]^2-1=-239/729