化简:cos^4a-sin^4a=
化简(1-sin^6 a-cos^6 a)/(cos^2 a-cos^4 a)==
化简cos^4(a/2)-sin^4(a/2)=
化简:cos^4a-sin^4a=
1-sin^6a-cos^6a分之1-sin^4a-cos^4a 化简
化简1-sin^4a-cos^4a/1-sin^6a-cos^6a
(1-sin^6a-cos^6a)/(1-sin^4a-cos^4a)=?
化简 1-sin^4a-cos^4a/cos^2a-cos^4a
化简 sin^4a-cos^4b
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
(cos a)^4+(sin a)^2*(sin a)^2+(sin a)^2=?
sin(a)*cos(a)=4,那么sin(a) cos(b)=?