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Question Number 158839 by EbrimaDanjo last updated on 09/Nov/21

Evaluate the following integrals using  integration By Parts  1. ∫_((π )/4) ^(π/2) xcsc^2 xdx    2. ∫_1 ^(√3) arctan((1/x))dx

EvaluatethefollowingintegralsusingintegrationByParts1.π4π2xcsc2xdx2.13arctan(1x)dx

Answered by gsk2684 last updated on 09/Nov/21

  ∫_(π/4) ^(π/2) x cosec^2 x dx  =[x∫ cosec^2 x dx−∫( (d/dx)x)(∫cosec^2 x dx)dx]_(π/4) ^(π/2)   =[x∫ cosec^2 x dx−∫(1)(−cot  x)dx]_(π/4) ^(π/2)   =[x(−cot x)+∫cot xdx]_(π/4) ^(π/2)   =[−x cot x+log  sin x]_(π/4) ^(π/2)   =[−(π/2) cot (π/2)+log  sin (π/2)]      −[−(π/4) cot (π/4)+log  sin (π/4)]  =[−(π/2) (0)+log  1]       −[−(π/4)(1)+log  (1/( (√2)))]  =[0+0] −[−(π/4)−log (√2)]  = (π/4)+log (√2)= (π/4)+log 2^(1/2)   = (π/4)+(1/2)log 2                     .......gsk...India....

π2π4xcosec2xdxMissing \left or extra \rightMissing \left or extra \rightMissing \left or extra \rightMissing \left or extra \right=[π2cotπ2+logsinπ2][π4cotπ4+logsinπ4]=[π2(0)+log1][π4(1)+log12]=[0+0][π4log2]=π4+log2=π4+log212=π4+12log2.......gsk...India....

Answered by puissant last updated on 09/Nov/21

K=∫_1 ^(√3) arctan((1/x))dx   IBP →  { ((u=arctan((1/x)))),((v′=1   )) :} ⇒  { ((u′=((−(1/x^2 ))/(1+(1/x^2 ))))),((v=x)) :}  ⇒ K=[xarctan((1/x))]_1 ^(√3) +∫_1 ^(√3) (x/(1+x^2 ))dx  ⇒ K={(√3)arctan(((√3)/3))−(π/4)}+(1/2)[ln(1+x^2 )]_1 ^(√3)   ⇒ K= (((√3)π)/6)−(π/4)+ln2                    ∴∵      K = π(((√3)/6)−(1/4))+ln2..                   .................Le puissant................

K=13arctan(1x)dxIBP{u=arctan(1x)v=1{u=1x21+1x2v=xK=[xarctan(1x)]13+13x1+x2dxK={3arctan(33)π4}+12[ln(1+x2)]13K=3π6π4+ln2∴∵K=π(3614)+ln2...................Lepuissant................

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