cos^2A-sin^2A/cos^2A+sin^2A会等于1-tan^2A/1+tan^2A呢?注明所用公式,

化简(sin a^2/cos a +cos a)*cot a sin/cos^2a+cos/sin^2a最小值 求证1+sin a+cos a+2sin acos a/1+sin a+cos a=sin a+cos a sin^2(a+pai)-cos(pai+a)*cos(-a)+1 sin^4+sin^2cos^2+cos^2a= 求证:sin 2a/1+sin a+cos a=sin a+cos a-1急 一个简单的三角函数题(sin a + cos a)/(sin a - cos a) 则 sin a *cos a=(sin a + cos a)/(sin a - cos a) = 2 则 sin a *cos a= 证明Cos^A-Sin^A=1-2Sin^A=2Cos^A-1=cos^a-sin^a 化简cos(a+b)cos(a-b)+sin^2b 化简sin^2a-cos^2a cos^2a+sin^2a=? sin^2A/cos^2A=? 化简sin(a/2)cos(a/2) 求证 1+sin a+cos a+2sin a*cos a/1 +sin a +cos a = sin a+ cos a 有什么思路! 化简 1-sin^4a-cos^4a/cos^2a-cos^4a 化简(1-sin^6 a-cos^6 a)/(cos^2 a-cos^4 a)== tan a=2,(3sin a-cos a)/(2sin a+cos a)= 已知tan a=2,求sin a+cos a /cos a -sin a 的值