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find-ln-x-x-1-dx-




Question Number 38719 by maxmathsup by imad last updated on 28/Jun/18
find   ∫  ln((√x) +(√(x+1)))dx
findln(x+x+1)dx
Answered by behi83417@gmail.com last updated on 29/Jun/18
I=xln((√x)+(√(x+1)))−∫x(((1/(2(√x)))+(1/(2(√(x+1)))))/( (√x)+(√(x+1))))dx=  =do−∫(x/(2(√x)(√(x+1))))dx=do−∫((√x)/(2(√(x+1))))dx  x=tg^2 t⇒dx=2tgt(1+tg^2 t)dt  ⇒∫((√x)/( (√(x+1))))dx=∫((tgt.2tgt(1+tg^2 t)dt)/(sect))=  =∫2tg^2 t.sectdt=2∫(sec^2 t−1)sectdt=  =2∫(sec^3 t−sect)dt=  =2(((sect.tgt)/2)+(1/2)∫sectdt−∫sectdt)=  =sect.tgt−ln(sect+tgt)+const  ⇒I=x.ln((√x)+(√(x+1)))−(1/2)(√x).(√(x+1))−  −(1/2)ln((√x)+(√(x+1)))+const. ■  I=(1/2)[(2x−1).ln((√x)+(√(x+1)))−(√(x^2 +x))]+const.
I=xln(x+x+1)x12x+12x+1x+x+1dx==dox2xx+1dx=dox2x+1dxx=tg2tdx=2tgt(1+tg2t)dtxx+1dx=tgt.2tgt(1+tg2t)dtsect==2tg2t.sectdt=2(sec2t1)sectdt==2(sec3tsect)dt==2(sect.tgt2+12sectdtsectdt)==sect.tgtln(sect+tgt)+constI=x.ln(x+x+1)12x.x+112ln(x+x+1)+const.◼I=12[(2x1).ln(x+x+1)x2+x]+const.
Commented by maxmathsup by imad last updated on 30/Jun/18
thank you sir Behi.
thankyousirBehi.

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