(sin a)/(1+cos a)=(1-cos a)/sin a怎么证sin a 1-cos a------ = -----------1+cos a sin a

求证1+sin a+cos a+2sin acos a/1+sin a+cos a=sin a+cos a 求证:sin 2a/1+sin a+cos a=sin a+cos a-1急 证明Cos^A-Sin^A=1-2Sin^A=2Cos^A-1=cos^a-sin^a 利用三角函数定义证明cos a-sin a+1/(cos a+sin a+1)=1-sin a/cos a 求证:sin a (1+cos2a)=sin a cos a (sin a)/(1+cos a)=(1-cos a)/sin a怎么证sin a 1-cos a------ = -----------1+cos a sin a 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! 证明恒等式tan a*sin a/tan a-sin a=1+cos a/sin a tan a/2=sin/1+cos a=1-cos a/sin a （1-sin^6a-cos^6a)/(1-sin^4a-cos^4a)=? 求证：tan a/2＝(1-cos)/sin a=sin a/(cos a+1) 求证 (cos a÷(1-sin a))=((1+sin a)÷cos a) sin a/(1+cos a)=1/2,求sin a+cos a sin 2a+2sin方a/ 1+tan a =2sin a cos a sin a+cos a=1/2.那么sin a*cos a= 已知 sin a-cos a=1/2,则 sin^3 a-cos^3 a 化简tan a(cos a-sin a)+sin a(sin a+tan a)/1+cos a 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