求证:sin 2a/1+sin a+cos a=sin a+cos a-1
求证:sin a (1+cos2a)=sin a cos a
求证:tan a/2=(1-cos)/sin a=sin a/(cos a+1)
证明Cos^A-Sin^A=1-2Sin^A=2Cos^A-1=cos^a-sin^a
求证sin^4a+cos^4a=1-2sin²acos²a
求证sin(90+a)=cos a
求证 2(1-sin a)(1+cos a)=(1-sin a + cos a)^2
求证:2[1+sin(派+a)][1+cos(-a)]=[1-sin(派-a)-cos(派-a)]
化简Sin A + Sin 2A / 1+cos A +
求证:sin a(1+tan a)+cos a(1+1/tan a)=1/sin a+1/cos a
tan a/2=sin/1+cos a=1-cos a/sin a
已知 sin a-cos a=1/2,则 sin^3 a-cos^3 a
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