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 证明sin(a+b)sin(a-b)=sin^2 a-sin^2 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sina sin(a+2b) - sinb sin(b+2a) =sin(a+b)sin(a-b) 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 三角形ABC 证明sin(A/2)*sin(B/2)*sin(C/2) 证明 SIN²A+SIN²B-SIN²C=2SINASINBCOSC 怎样证明/sin a +sin b/ 求证:sin(a+b)sin(a-b)=sin^2a-sin^2b 证明sin(A+B)sin(A-B)=cos^2B-cos^2A 证明三角函数等式sin(A+B)-sinA=2cos(A+B/2)sin(B/2) 已知sin(a)=2sin(b)求sin(a/2)/sin(b/2)的值. cos2B-cos2A=-2sin(A+B)sin(B-A) 为什么,证明 三角函数!证明1/2(cos2B-cos2A)=sin(A+B)×sin(A-B) 如何证明sin(a+b)sin(a-b)=sin*a-sin*b (*为平方) 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) 证明：三角形ABC中,若sin²A+sin²B+sin²C＜2,三角形ABC为钝角三角形