已知sin(a-b)=5/13,sin(a+b)=-5/13,且a-b属于（2分之派,派）,a+b属于（2分之3派,2派）,求cos2b的值

已知3SIN^2A+2SIN^2B=5SINA,求SIN^2A+SIN^2B范围 已知sin(a)=2sin(b)求sin(a/2)/sin(b/2)的值. 3 在三角形ABC中,已知（a2+b2）sin（A-B）=（a2-b2）sin(A+B) 求证：ABC是等腰或直角三角形(a^2+b^2)sin(A-B)=(a^2-b^2)sin(A+B),(sin^A+sin^B)sin(A-B)=(sin^A-sin^B)sin(A+B) sin^A*(sin(A+B)-sin(A-B))=sin^B*(sin(A-B)+sin(A+B)) sin^A*2c 已知sinA=1/5,求2sin(A+B)cosA-sin(2A+B) 已知sin(a+b)等于2/3,sin(a-b0 =1/5,求tana:tanb 三角形ABC中,已知COS A =3/5,SIN B=5/13,求SIN C的值 sin(a+b)cosa-cos(a+b)sina=5/13 则sin（π-B)=? 已知sin(a+b)=-3/5,cos(a-b)=12/13,且π/2 已知sin(A+B)=3/5,sin(A-B)=1/5,证明：tan A=2tan B. 已知a,b都是锐角,sin a =4/5,cos(a+b),求sin b 的值,速求! 已知a b为锐角,且cosa=5/13,sin(a-b)=-3/5,求sin(2a-b) 已知a,b属于(3π/4,π),sin(a+b)=-3/5,sin(b-π/4)=12/13,则cos(a+4/π)= 已知a,b属于(3pai/4,pai),sin(a+b)=-3/5,sin(b-pai/4)=12/13则cos(a+pai/4)=多少 已知a,b,属于（3pi/4,pi),sin(a+b)=-3/5,sin(b-pi/4)=12/13,则cos(a+pi/4)=? 已知A B属于3π/4到π,SIN(A+B)=-3/5,SIN(B-π/4)=12/13,求COS(A+π/4 已知cos(45-a)=3/5,sin(225+b)=-12/13,a(45,135),b(0,45),求sin(a+b)值 已知sin(45度-a)=5/13,求sin(25pai/4 + a) 求解 已知 sin(a+b)=1/2 ,sin(a_b)=1/3,求证:tan a=5tan b求解:已知 sin(a+b)=1/2 ,sin(a_b)=1/3,求证:tan a=5tan b