证明 sin^4a+cos^4a=1-2sin^2a乘以cos^2a
证明sin(4A)sin(2A)(1-cos(2A)) cos(4A)cos(2A)(1 cos(2A))=cos(2A
若sin^4a/sin^2b+cos^4a/cos^2b=1,证明sin^4b/sin^2a+cos^4b/cos^2a
证明Cos^A-Sin^A=1-2Sin^A=2Cos^A-1=cos^a-sin^a
证明tan a/2=sin a/(1+cos a)
化简(1-sin^6 a-cos^6 a)/(cos^2 a-cos^4 a)==
证明:cos^4 a-sin^4 a=cos^2 a(1-tan a)(1+ tan a)
证明: sin^2a+cos^2a=1
tan a/2=(1-cos a)/sin a=sin a/(1+cos a)如何证明?
化简 1-sin^4a-cos^4a/cos^2a-cos^4a
(cos a)^4+(sin a)^2*(sin a)^2+(sin a)^2=?
(1-sin^6a-cos^6a)/(sin^2a-sin^4a)
已知tan a=-1/3,求4sin a-2cos a/5cos a+3sin a=