证明sin(A+B)sin(A-B)=cos^2B-cos^2A

用正弦定理证明a+b/c=sin A+sin B/sin c 证明sin(a+b)sin(a-b)=sin^2 a-sin^2 b, 如何证明sin(a+b)sin(a-b)=sin*a-sin*b (*为平方) 【证明】Sin A+sin B=2Sin 22 证明 SIN²A+SIN²B-SIN²C=2SINASINBCOSC a（sin B－sin C）＋b（sin C＋sin A）＋c（sin A－sin B）=0 请证明...不好意思.我写错了.a（sin B－sin C）＋b（sin C—sin A）＋c（sin A－sin B）=0 怎样证明/sin a +sin b/ 证明sina sin(a+2b) - sinb sin(b+2a) =sin(a+b)sin(a-b) 如何证明sin(a+b)=sin(a)cos(b)+cos(α)sin(b) 懂得进.证明,sina+sin(a+b)+sin(a+2b)+...sin(a+nb)=sin(a+ab/2)sin[(n+1)b/2]/sin(b/2) 证明sin(a+b)=sinacosb+cosasinb 证明sin(A+B)=sinAcosB+cosAsinB 证明 sin^2A+sin^2B-sin^2A*sin^2B+cos^2A*cos^2证明 sin^2A+sin^2B-sin^2A*sin^2B+cos^2A*cos^2B=1 如何证明在任何三角形ABC中 周长等于 a/sin A (sin A +sin B +sin C) 三角形ABC 证明sin(A/2)*sin(B/2)*sin(C/2) 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 三角形ABC中证明 COSA+COSB+COSC=1+4SIN(A/2)*SIN(B/2)*SIN(C/2) 三角形ABC中证明 COSA+COSB+COSC=1+4SIN(A/2)*SIN(B/2)*SIN(C/2)