cos(45-a)•cos(45+a)=1/3,sin^4 a+cos^4 a=____
化简(1-sin^6 a-cos^6 a)/(cos^2 a-cos^4 a)==
证明sin(4A)sin(2A)(1-cos(2A)) cos(4A)cos(2A)(1 cos(2A))=cos(2A
(1-sin^6a-cos^6a)/(1-sin^4a-cos^4a)=?
若sin^4a/sin^2b+cos^4a/cos^2b=1,证明sin^4b/sin^2a+cos^4b/cos^2a
已知tan a=-1/3,求4sin a-2cos a/5cos a+3sin a=
已知sin a+cos a=m求cos a-sin a(45
已知 sin a-cos a=1/2,则 sin^3 a-cos^3 a
已知(4sin a-2cos a)/(5cos a +3sin a)=6/11,求cos^4 a-sin^4 a
已知sin a-2cos a=0 求4sin^2 a-3sin a x cos a-5cos^2 a的值
已知cosa=1/4,求sin(2π+a)cos(-π+a)/cos(-a)tana
若sina+sin^2a=1,求cos^2a+cos^4a的和
化简 1-sin^4a-cos^4a/cos^2a-cos^4a