sin(a+b)=1/2.cos(a-b)=1/3,求tana/tanb

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 sin(a-b)*cos a-cos(a-b)*sin a=1/5,则cos 2b的值是 由cos(a+b)=cos a cos b-sin a sin b cos(a-b)=cos a cos b+sin a sin b解题设a为锐角,证：1、2分之根3乘cos a + 2分之1乘sin a=cos(6分之π-a)2、cos a-sin a=根号2cos(4分之π+a) Cos(a+b)*cos(a-b)=1/5 求cos ^2-sin^2 如何证明sin(a+b)=sin(a)cos(b)+cos(α)sin(b) cos(a-b)cos(b-c)+sin(a-b)sin(b-c)= 已知 sin a +sin b =1/4cos a +cos b =1/3求 tan (a+b) 已知sin(a+b)sin(a-b)=-1/3,求cos^2a-cos^2b的值 cos^2a-cos^2b=m,那么sin(a+b)sin(a-b)=? cos²a-cos²b=c,则sin(a+b)sin(a-b)= cos∧a-cos∧b=t则sin(a+b)sin(a-b)= 证明sin(A+B)sin(A-B)=cos^2B-cos^2A 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 若cos(A+B)cos(A-B)=1/3 则cos平方A－sin平方B 等于 已知cos(a+b)cos(a-b)=1/3,则cos^2a-sin^2b的值是? 若cos(a+b)cos(a-b)=1/3,则cos²a-sin²b的值 cos(a+B)×cos(a-B)=1/3,求cos^2(a)-sin^2(B)的值 求证cos(a+b)cos(a－b)=cos^2b－sin^2a