已知:sin^2A/sin^2B+cos^2Acos^2C=1,求证:tan^2Acot^2B=sin^2C

已知tan(A-B)/tanA+sin^2C/sin^2A=1,求证：tanA*tanB=tan^2C 求证[1]1-2sin acos a/cos²a -sin²a =1-tan a/1+tan a.[ 求证:sin^2/(sin-cos) - (sin+cos)/(tan^2 -1) =sin+cos 求证sin^4a+cos^4a=1-2sin²acos²a 在三角形ABC中求证 aCOS A+bCOS B+cCOS C=2aSIN B SIN C 在△ABC中,求证：sin^2A+sin^2B+cos^2C+2sinAsinBcos(A+B)=1 已知tan a =-4,求下列各式的值 (1)sin^2 a (2)3sin acos a (3)cos^2 a-sin 已知tan^2A=2tan^B+1求证sin^2B=2sin^2A-1 已知sin^2B=2sin^2A-1求证tan^2A=2tan^B+1 已知tan^2 a=2tan^ B +1,求证sin^2 b=sin^2 a -1 已知tan(a-r)/tana+sin^2b/sin^2a=1 ,求证tan^2b=tana*tanr.. 求解 已知 sin(a+b)=1/2 ,sin(a_b)=1/3,求证:tan a=5tan b