sin(a+b)=-3/5,sin(b-派/4)=12/13,ab属于（3派/4,派）求cos(a+派/4)

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 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) 求证恒等式sin(A+B)sin(A-B)=sin²A-sin²B 求证:sin(a+b)sin(a-b)=sin^2a-sin^2b sin(A+B)=4/5,sin(A-B)=-3/5,则tanA/tanB= sin(a+b)=1/3,sin(a-b)=1/5,则tana*cotb=? 【证明】Sin A+sin B=2Sin 22 sin a-sin b等于 cos(a+b)cos(a-b)+sin(a+b)sin(a-b)=-3/5,求sin(3π/2+2b) 已知sin(a)=2sin(b)求sin(a/2)/sin(b/2)的值. 已知sin(A+B)=3/5,sin(A-B)=1/5,证明：tan A=2tan B. sin(a+b)sin(a-b)=sin2a-sin2b求证 求证：sin(A+B)sin(A-B)=sinAsinA-sinBsinB sin（a-b）=sin（a+b）吗? SIN(B-A)=-SIN(A-B)为啥 已知sin(a+b)等于2/3,sin(a-b0 =1/5,求tana:tanb