求证sin^4a=1/8(3-4cos^2a+cos4a)
三角比:[cos(4a-PAI/2)*sin(PAI/2-2a)]/[(1+cos2a)*(1+cos4a)]
化简[cos(4a-π/2)*sin(π/2-a)*cos2a]/[(1+cos2a)(1+cos4a)*cosa
三角函数证明题(1)3+cos4a-4cos2a=8sin~4次方 a(2)tanatanb/tan2a-tana +
求证sin^4a+cos^4a=1-2sin²acos²a
求证:tan a/2=(1-cos)/sin a=sin a/(cos a+1)
求证:sin a (1+cos2a)=sin a cos a
求证sin^4a-cos^4a=-cos2a
已知(4sin a-2cos a)/(5cos a +3sin a)=6/11,求cos^4 a-sin^4 a
已知tan a=-1/3,求4sin a-2cos a/5cos a+3sin a=
1.sin(a+45度)sin(45度-a)=1/3,求cos4a的值
证明:(3-4cos2A+cos4A)/(3+4cos2A+cos4A)=tan四次方A 要详解
化简(1-sin^6 a-cos^6 a)/(cos^2 a-cos^4 a)==