sin a-cos a=1/5 sin^2 a+cos^2 a=1
证明Cos^A-Sin^A=1-2Sin^A=2Cos^A-1=cos^a-sin^a
tan a/2=sin/1+cos a=1-cos a/sin a
求证:tan a/2=(1-cos)/sin a=sin a/(cos a+1)
已知 sin a-cos a=1/2,则 sin^3 a-cos^3 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
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=
Cos(a+b)*cos(a-b)=1/5 求cos ^2-sin^2
证明tan a/2=sin a/(1+cos a)
已知2cos∧2 a+3cos a sin a-3sin∧2 a=1,求:tan a,(2sin a-3cos a)\(
为什么 tan a +1/tan a=sin^2 a +cos^2 a/(sina cos a)