求证[1]1-2sin acos a/cos²a -sin²a =1-tan a/1+tan a.[
求证[1]1-2sin acos a/cos²a -sin²a =1-tan a/1+tan a.[
求证:tan a/2=(1-cos)/sin a=sin a/(cos a+1)
求证sin^4a+cos^4a=1-2sin²acos²a
证明恒等式tan a*sin a/tan a-sin a=1+cos a/sin a
求证:sin a(1+tan a)+cos a(1+1/tan a)=1/sin a+1/cos a
为什么 tan a +1/tan a=sin^2 a +cos^2 a/(sina cos a)
证明tan a/2=sin a/(1+cos a)
已知tan a =-4,求下列各式的值 (1)sin^2 a (2)3sin acos a (3)cos^2 a-sin
求证:sin^2A+cos^2A+sinAcosA/sin^2A+cos^2A=tan^2A+1+tanA/tan^2A
求证1/(sin^2)a+1/(cos^2)a-1/(tan^2)a=2+(tan^2)a
tan a/2=sin/1+cos a=1-cos a/sin a
求证1+2sin a cos a/cos^2 a-sin^2 a=1+tan a/1-tan a