证明2sin(π+a)cos(π-a)=sin(2a)
证明Cos^A-Sin^A=1-2Sin^A=2Cos^A-1=cos^a-sin^a
化简:sin(-a)cos(2π+a)sin(-a-π)
证明tan a/2=sin a/(1+cos a)
化简[cos(a-π)/sin(π-a)]sin(a-π/2)cos(π/2+a)=
若sin^4a/sin^2b+cos^4a/cos^2b=1,证明sin^4b/sin^2a+cos^4b/cos^2a
证明: sin^2a+cos^2a=1
证明sin(4A)sin(2A)(1-cos(2A)) cos(4A)cos(2A)(1 cos(2A))=cos(2A
tan a/2=(1-cos a)/sin a=sin a/(1+cos a)如何证明?
证明 sin^2A+sin^2B-sin^2A*sin^2B+cos^2A*cos^2
sin(2π-a)cos(π/2-a)/cos(π-a)sin(π/2+a)
化简sin(π+a)cos(-a)+sin(2π-a)cos(π-a)
化简 sin(2π-a)sin(π+a)cos-π-a) / sin(3π-a)cos(π-a)