证明:(1+tan a+cot a)/(1+tan^2 a+tan a)-cot a/(1+ tan^2 a)=sin
证明:(1+tan a+cot a)/(1+tan^2 a+tan a)-cot a/(1+ tan^2 a)=sin
证明(tan^2a+tana+1)(cot^2a+cota+1)=tan^2a+cot^2a+1
怎么证明tan^2A+cot^2A不等于1
化简 (cot a/2 -tan a/2)(1+ tan a * tan a/2)
如何证明cot(1/2A)-tan(1/2A)=2cot(A)
tan(a/2)+cot(a/2)=?
化简:cot^a(tan^a-sin^a)
化简cot^2 A(tan^2 A-sin^2 A)
化简:cot^2A(tan^2A-sin^2A)
(cot (a/2) -tan (a/2))^2(1-tan a / tan (2a))
(sin a+tan a)(cos a+cot a)等于(1+sin a)(1+cos a) 证明恒等式成立
证明:(tan a-cot a)/(sec a+csc a)=sin a-cos a