分子= sin(3x+x)+sin(3x-x)
=sin3xcosx+cos3xsinx+sin3xcosx-cos3xsinx
=2sin3xcosx
同理,分母=2cos3xcosx
所以左边=sin3x/cos3x=tan3x=右边
证明(sin4x+sin2x)/(cos4x+cos2x)=tan3x
2个回答
相关问题
-
已知tan(x-π/4）=2 求（sin2x+cos2x）/（2cos²x-3sin2x-1)
-
求证（cos^2x-sin^2x)(cos^4x+sin^4x）+1/4sin2xsin4x=cos2x
-
（sin3xsinx）sin2x+（cos3xcosx）cos2x =1/ 2 [（cos2x-cos4x）sin2x+
-
化简[1-(sin^4x-sin^2cos^2x+cos^4x)/(sin^2)]+3sin^2x
-
化简sin(3π-x)cos(x-3/2)cos(4π-x)/tan(x-5π)cos(π/2+x)sin(x-5/2π
-
已知tan(x-π/4）=2求（sin2x+cos2x）/（2cos方-3sin2x-1)
-
S=(cos^2 x+cos^4 x+.+cos^2n x)+(sin^2x+sin^4 x+.+sin^2n x)数列
-
若4sin2x-6sinx-cos2x+3cosx=0．求：[cos2x−sin2x(1−cos2x)(1−tan2x)
-
已知tan(x-π/4),求(sin2x+2cos2x)/(2cos²x-3sin2x-1)的值
-
1.y=cos^4x+sin^4x 求周期 2.y=（sin2x+sin（2x+π/3)）/（ cos2x+cos（2x