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Question Number 118668 by bemath last updated on 19/Oct/20

  ∫ ((x∣sin x∣)/(1+cos^2 x)) dx ?

xsinx1+cos2xdx?

Answered by Lordose last updated on 19/Oct/20

Ω=∫ ((x∣sinx∣)/(sin^2 x))dx  Ω=∫x∣cosecx∣dx   IBP {u=x dv=cosecxdx}  Ω = xln∣tan((x/2))∣ − ∫ln∣tan((x/2))∣dx  Δ=∫ln∣tan((x/2))∣dx  Δ=2∫ln∣tan(u)∣du  {u=(x/2)}  Δ=2∫ln∣((−ie^(iu) (1−e^(−2iu) ))/(e^(iu) (1+e^(−2iu) )))∣du  Δ=2(∫ln∣−i∣du + ∫ln∣1−e^(2iu) ∣du − ∫ln∣1+e^(−2iu) ∣du)  y=e^(−2iu)  ⇒ du=((idy)/(2y))  Δ = 2(((iπu)/2)  + (i/2)∫ ((ln∣1−y∣)/y)dy − (i/2)∫ ((ln∣1−y∣)/y)dy  Δ= iπu + iLi_2 (y)−iLi_2 (−y) + C  Δ=i(πu + Li_2 (e^(−2iu) ) − Li_2 (−e^(−2iu) ))+ C  Ω= xln∣tan((x/2))∣−i(((πx)/2) + Li_2 (e^(−ix) ) − Li_2 (−e^(ix) )) + C  Check for errors!

Ω=xsinxsin2xdxΩ=xcosecxdxIBP{u=xdv=cosecxdx}Ω=xlntan(x2)lntan(x2)dxΔ=lntan(x2)dxΔ=2lntan(u)du{u=x2}Δ=2lnieiu(1e2iu)eiu(1+e2iu)duΔ=2(lnidu+ln1e2iuduln1+e2iudu)y=e2iudu=idy2yΔ=2(iπu2+i2ln1yydyi2ln1yydyΔ=iπu+iLi2(y)iLi2(y)+CΔ=i(πu+Li2(e2iu)Li2(e2iu))+CΩ=xlntan(x2)i(πx2+Li2(eix)Li2(eix))+CCheckforerrors!

Commented by bemath last updated on 19/Oct/20

thank you sir

thankyousir

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