已知sin(a)=2sin(b)求sin(a/2)/sin(b/2)的值.

已知sin(a)=2sin(b)求sin(a/2)/sin(b/2)的值. 已知3SIN^2A+2SIN^2B=5SINA,求SIN^2A+SIN^2B范围 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sin(A+B)=2/3,sin(A-B)=1/5.求tanA/tanB 已知sin(a+b)=1/2,sin（a-b)=1/3,求tana/tanb 已知sinA=1/5,求2sin(A+B)cosA-sin(2A+B) 三角形ABC中,已知（sin^2 A-sin^2 B-sin^2 C)/(sinB sinC)=1 求A? 关于三角函数的问题 已知3sin^2a+2sin^b=2sina,求sin^2a+sin^b的取值范围 已知3sin²a-2sina+2sin²b=0.试求sin²a+sin²b的取值范围 已知sin(a+b)等于2/3,sin(a-b0 =1/5,求tana:tanb 【证明】Sin A+sin B=2Sin 22 sin^2 A=sin^2 B+sinBsinC+sin^2 C 求A角 证明sin(a+b)sin(a-b)=sin^2 a-sin^2 b, 求证:sin(a+b)sin(a-b)=sin^2a-sin^2b 已知 sin a,sin 2x ,cos a 成等差数列,sin a ,sin x ,cos a 成等比数列,求cos 2x 的值.已知 ,3sin^2 a+2sin^2 b=1 ,3sin 2a-2sin 2b=0 且a ,b 为锐角,试求 a+2b的值. 已知 tan a =1 3sin(a+b)=sin(2a+b) ,求 tan(a+b) 的 值. 求 sin(a+b)=? 已知sin(a+b)sin(a-b)=-1/3,求cos^2a-cos^2b的值