-如何由2=sin^2a/cos^2a,sin^2a-cos^2a=1这两条式子算出sin^2a和cos^2a
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
已知tan a=2,求sin a+cos a /cos a -sin a 的值
tan a/2=(1-cos a)/sin a=sin a/(1+cos a)如何证明?
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
化简Sin A + Sin 2A / 1+cos A +
化简[cos(a-π)/sin(π-a)]sin(a-π/2)cos(π/2+a)=
已知2cos∧2 a+3cos a sin a-3sin∧2 a=1,求:tan a,(2sin a-3cos a)\(