[TEX]D=sin^5x-\frac{sin5x}{16}+\frac{5.sin3x}{16}-\frac{5.sinx}{8}[/TEX]
[TEX]D=\frac{16.sin^5x-sin5x+5.sin3x-10.sinx}{16}[/TEX]
ta biến đổi
[TEX]16.sin^5x-sin5x+5.sin3x-10.sinx[/TEX]
[TEX]=16.sin^5x-sin(3x+2x)+5.sin3x-10.sinx[/TEX]
[TEX]=16.sin^5x-sin3x.cos2x-sin2x.cos3x+5.sin3x-10.sinx[/TEX]
[TEX]=16.sin^5x-(3.sinx-4.sin^3x).(1-2.sin^2x)-sin2x.(4.cos^3x-3.cosx)+5.sin3x-10.sinx[/TEX]
[TEX]=16.sin^5x-(3.sinx-6.sin^3x-4.sin^3x+8.sin^5x)-2.sinx.cosx.(4.cos^3x-3.cosx)+5.(3.sinx-4.sin^3x)-10.sinx[/TEX]
[TEX]=8.sin^5x-3.sinx+10.sin^3x-(8.sinx.cos^4x-6.sinx.cos^2x)+15.sinx-20.sin^3x-10.sinx[/TEX]
[TEX]=8.sin^5x+2.sinx-10.sin^3x-8.sinx.cos^4x+6.sinx.cos^2x[/TEX]
[TEX]=8.sin^5x+2.sinx-10.sin^3x-8.sinx.(1-sin^2x)^2+6.sinx.(1-sin^2x)[/TEX]
[TEX]=8.sin^5x+2.sinx-10.sin^3x-8.sinx.(1-2.sin^2x+sin^4x)+6.sinx-6.sin^3x[/TEX]
[TEX]=8.sin^5x+2.sinx-10.sin^3x-8.sinx+16.sin^3x-8.sin^5x+6.sinx-6.sin^3x[/TEX]
[TEX]=0[/TEX]
vậy
[TEX]D=\frac{16.sin^5x-sin5x+5.sin3x-10.sinx}{16}=0[/TEX]
[TẶNG BẠN] TRỌN BỘ Bí kíp học tốt 08 môn
