1:sin(a-b)=sin(-b+a)2:sin(a-b)=sin(-（b-a）),这个为什么是这样的?知识点忘了.

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)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-sin b等于 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 【证明】Sin A+sin B=2Sin 22 已知sin(a)=2sin(b)求sin(a/2)/sin(b/2)的值. 在△ABC中,求证；sin^(A/2)+sin^(B/2)+sin^(C/2)=1-2sin(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 sin²a+sin²b-sina²sin²b+cos²cosb=1 证明等式恒成立 sin^a+sin^b-sin^asin^b+cos^acos^b=1sin^a+sin^b-sin^asin^b+cos^acos^b=1 只需证sin^a(1-sin^b)+sin^b+cos^acos^b=1 只需证sin^acos^b+cos^acos^b+sin^b=1 这里到这里没有看懂 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 求 sin(a+b)=?