\int_{}^{}sinx.cos3x dx =****************************?????????
ai giúp mình giải bài này với !!!!!!!!!!!!!!!!!!!!!
[TEX]\int\limits_{}{}sinx(4cos^3x-3cosx)dx[/TEX]
[TEX]\int\limits_{}{}(4sinxcos^3x-3sinxcosx)dx[/TEX]
[TEX]\int\limits_{}{}4sinxcos^3xdx-\int\limits_{}{}3sinxcosx)dx=I1-I2[/TEX]
[TEX]I1=\int\limits_{}{}4sinxcos^3xdx[/TEX]
[TEX]\int\limits_{}{}2sin2xcos^2xdx[/TEX]
[TEX]\int\limits_{}{}sin2x(1+cos2x)dx[/TEX]
[TEX]\int\limits_{}{}sin2x+sin2xcos2x)dx[/TEX]
[TEX]\int\limits_{}{}sin2xdx+\int\limits_{}{}sin2xcos2xdx[/TEX]
[TEX]\frac{-cos2x}{2}+\int\limits_{}{}\frac{1}{2}sin2xdsin2x[/TEX]
[TEX]\frac{-cos2x}{2}+\frac{1}{4}(sin2x)^2[/TEX]
[TEX]I2=\int\limits_{}{}3sinxcosx)dx[/TEX]
[TEX]\int\limits_{}{}3sinxdsinx[/TEX]
[TEX]I2=\frac{3sin^2x}{2}[/TEX]