知sin(A+B)=1/3,sin(A-B)=1/4.求(cosA)的平方-(cosB)的平方=?

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 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) 3sin(a)^2+2sin(b)^2=1,3sin(a)=2sin(b),a,b都为锐角,求a+2b的值是3sin(2a)=2sin(2b), 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+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 【证明】Sin A+sin B=2Sin 22 sinA=1/2,sinB=1/3,sin(A+B)sin(A-B)=? sin(a+b)=1/2,sin(a-b)=1/3,则tana/tanb=? sin(a+b)=1/2,sin(a-b)=1/3,则tana/tanb=? sin(a+b)=1/3,sin(a-b)=1/5,则tana*cotb=? 已知sin(a+b)=1/2,sin（a-b)=1/3,求tana/tanb sin(a-b)=1,sin a=1/3,求cos b的值RT sin(a-b)=1 ,sin a=1/3 ,求cos b的值 sin(a+b)=1/4,sin(a-b)= 1/3,则tana/tanb等于? 已知sin(A+B)=2/3,sin(A-B)=1/5.求tanA/tanB