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[TEX]1) \int tan^8xdx= \int [tan^6x(tan^2x+1)-tan^4x(tan^2x+1)+tan^2x(tan^2x+1)-(tan^2x+1)+1]dx[/TEX]
[TEX]= \int (tan^6x-tan^4x+tan^2x-1)(tan^2x+1)dx+ \int dx[/TEX]
[TEX]= \int (tan^6x-tan^4x+tan^2x-1)dtanx+x= \frac{1}{7}tan^7x- \frac{1}{5}tan^5x+ \frac{1}{3}tan^3x-tanx+x+C[/TEX]

[TEX]2) \int ln(1+x)dx= \int ln(1+x)d(x+1)= (x+1)ln(x+1)- \int \frac{x+1}{x+1}dx[/TEX]
[TEX]=(x+1)ln(x+1)-x+C[/TEX]
Chú ý: Đặt u=ln(x+1), dv=dx \Rightarrow [TEX]u= \frac{1}{x+1}, v=x+1[/TEX]
 
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