求证(1-tan^4A)cos^2A+tan^2A=1
求证:tan a/2=(1-cos)/sin a=sin a/(cos a+1)
求证[1]1-2sin acos a/cos²a -sin²a =1-tan a/1+tan a.[
求证:cos^2a/[cot(a/2)-tan (a/2)]=1/4sin2a
为什么 tan a +1/tan a=sin^2 a +cos^2 a/(sina cos a)
求证1/(sin^2)a+1/(cos^2)a-1/(tan^2)a=2+(tan^2)a
证明:cos^4 a-sin^4 a=cos^2 a(1-tan a)(1+ tan a)
求证:sin^2A+cos^2A+sinAcosA/sin^2A+cos^2A=tan^2A+1+tanA/tan^2A
求证:sin a(1+tan a)+cos a(1+1/tan a)=1/sin a+1/cos a
证明tan a/2=sin a/(1+cos a)
求证:tan(a+b)-tana\1+tanatan(a+b)=sin2b\2cos^2b
求证1+2sin a cos a/cos^2 a-sin^2 a=1+tan a/1-tan a
证明:(1+tan a+cot a)/(1+tan^2 a+tan a)-cot a/(1+ tan^2 a)=sin