求证 (cos a÷(1-sin a))=((1+sin a)÷cos a)

求证 (cos a÷(1-sin a))=((1+sin a)÷cos a) 求证1+sin a+cos a+2sin acos a/1+sin a+cos a=sin a+cos a 求证:sin a (1+cos2a)=sin a cos a 求证:sin 2a/1+sin a+cos a=sin a+cos a-1急 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! 求证：tan a/2＝(1-cos)/sin a=sin a/(cos a+1) 求证sin^4a+cos^4a=1 求证:sin a(1+tan a)+cos a(1+1/tan a)=1/sin a+1/cos a 求证3-sin^4a-cos^4a/2cos^a=1+tan^a+sin^a 速答 谢谢 求证2cos^2a+sin^4a=cos^4a+1 求证：cos^8A-sin^8A=cos2A(1-1/2sin^2A) 求证sin^4a+cos^4a=1-2sin^2acos^2a 求证sin^6A+cos^6A=1-3sin^2Acos^A 求证(1-sin^2Acos^2A)(cos2A)=cos^6A-sin^6A 求证:2[1+sin(派+a)][1+cos(-a)]=[1-sin(派-a)-cos(派-a)] 求证 2（1-sin a）（1+cos a）=（1-sin a + cos a）^2 求证1/sin^2a+3/cos^2a>=4+2根号下31/sin²a +3/cos²a=(sin²a+cos²a)/sin²a +3(sin²a+cos²a)/cos²a=1+cos²a/sin²a+3+3sin²a/cos²a=4+cos²a/sin²a+3sin²a/cos²a≥4+2√[(cos 以知cos(a+β )=-1,求证sin(2a+β )+sinβ=0