sin(a-b)=1,sin a=1/3,求cos b的值RT

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^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 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), 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 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 sin(a+b)=0.5,sin(a-b)=1/3 则tana/tanb 已知sin(a+B)sin(a-B)=1/3,求cos2b-cos2a 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