证明: sin^2a+cos^2a=1
证明Cos^A-Sin^A=1-2Sin^A=2Cos^A-1=cos^a-sin^a
证明tan a/2=sin a/(1+cos a)
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
若sin^4a/sin^2b+cos^4a/cos^2b=1,证明sin^4b/sin^2a+cos^4b/cos^2a
tan a/2=(1-cos a)/sin a=sin a/(1+cos a)如何证明?
证明1-COS^2α/(SINα-COSα)-SINα+COSα/(TAN^2a-1)=SINa+COSa
证明:cos^4 a-sin^4 a=cos^2 a(1-tan a)(1+ tan a)
sin^2a+sin^2β-sin^2a*sin^2β+cos^2a*cos^2β=1 证明恒等式?各位高手 教教我
已知 a为第二象限,证明:2sinαcosα/(sinα+cosα-1)(sinα+cosα+1)=(1+cosα)/s
利用三角函数定义证明cos a-sin a+1/(cos a+sin a+1)=1-sin a/cos a
证明恒等式tan a*sin a/tan a-sin a=1+cos a/sin a