(1-tan^4A)cos^2A+tan^2A=1
为什么 tan a +1/tan a=sin^2 a +cos^2 a/(sina cos a)
证明:cos^4 a-sin^4 a=cos^2 a(1-tan a)(1+ tan a)
证明tan a/2=sin a/(1+cos a)
证明:(1+tan a+cot a)/(1+tan^2 a+tan a)-cot a/(1+ tan^2 a)=sin
求证[1]1-2sin acos a/cos²a -sin²a =1-tan a/1+tan a.[
已知tan(a+b)=2/5,tan(b-pai/4)=1/4,求(cos a+sin a)/(cos a-sin a)
tan a/2=sin/1+cos a=1-cos a/sin a
求证:tan a/2=(1-cos)/sin a=sin a/(cos a+1)
已知tan(π/4+已知tan (π/4+a)=3 求 sin2a-2cos^2a-1的值
已知tan a=-1/3,求4sin a-2cos a/5cos a+3sin a=
求证1/(sin^2)a+1/(cos^2)a-1/(tan^2)a=2+(tan^2)a
tan a+1 /1-tan a =3+2√2,求sin a和cos a的值.