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Question Number 44781 by arvinddayama01@gmail.com last updated on 04/Oct/18
prove that:− ∫(1/(t(√(1−t^2 ))))dt = ln(1−(√(1−t^2 )))+C
provethat:1t1t2dt=ln(11t2)+C
Answered by tanmay.chaudhury50@gmail.com last updated on 04/Oct/18
∫((tdt)/(t^2 (√(1−t^2 )) ))  k^2 =1−t^2    2kdk=−2tdt  ∫((−kdk)/((1−k^2 )k))  ∫(dk/(k^2 −1))  (1/2)∫(((k+1)−(k−1))/((k+1)(k−1)))dk  (1/2)∫(dk/(k−1))−(1/2)∫(dk/(k+1))  (1/2){ln(k−1)−ln(k+1)}+c  (1/2){ln(((k−1)/(k+1)))}+c  (1/2){ln((((√(1−t^2 )) −1)/( (√(1−t^2 )) +1)))}+c←correct answer  recheck of answer given RHS  (d/dt){ln(1−(√(1−t^2 ))  )}  (1/(1−(√(1−t^2 )) ))×((0−(1/(2(√(1−t^2 )) ))×−2t)/1)  (1/(1−(√(1−t^2 )) ))×(t/( (√(1−t^2 ))))  now recheck result obtained  (d/dt)[(1/2){ln((√(1−t^2 )) −1)−ln((√(1−t^2 )) +1)}]  (1/2)[{(1/( (√(1−t^2 ))  −1))×(1/(2(√(1−t^2 ))  ))×−2t}−{(1/( (√(1−t^2 )) +1))×((−2t)/(2(√(1−t^2 )) ))}]  (1/2)[((−t)/( (√(1−t^2 )) .((√(1−t^2 )) −1)))+(t/( (√(1−t^2 )) .((√(1−t^2 ))  +1)))]  (t/(2(√(1−t^2 )) )){((−1)/( (√(1−t_ ^2 ))  −1))  +(1/( (√(1−t^2 )) +1)) }  (t/(2(√(1−t^2 )))){(((√(1−t)) −1−(√(1−t^2 ))  −1)/((1−t^2 −1))}  (1/2)×(t/( (√(1−t^2 )))){((−2)/(−t^2 ))}  (1/(t(√(1−t^2 ))))  so attached answer in right hand side  ln(1−(√(1−t^2 ))  ) is not correct
tdtt21t2k2=1t22kdk=2tdtkdk(1k2)kdkk2112(k+1)(k1)(k+1)(k1)dk12dkk112dkk+112{ln(k1)ln(k+1)}+c12{ln(k1k+1)}+c12{ln(1t211t2+1)}+ccorrectanswerrecheckofanswergivenRHSddt{ln(11t2)}111t2×0121t2×2t1111t2×t1t2nowrecheckresultobtainedddt[12{ln(1t21)ln(1t2+1)}]12[{11t21×121t2×2t}{11t2+1×2t21t2}]12[t1t2.(1t21)+t1t2.(1t2+1)]t21t2{11t21+11t2+1}t21t2{1t11t21(1t21}12×t1t2{2t2}1t1t2soattachedanswerinrighthandsideln(11t2)isnotcorrect
Commented by arvinddayama01@gmail.com last updated on 06/Oct/18
thanks
thanks
Answered by ajfour last updated on 04/Oct/18
let  t=sin θ  ∫((cos θdθ)/(sin θcos θ)) = ∫cosec θdθ  =ln ∣cosec θ−cot θ∣+c  =ln ∣(1/t)−((√(1−t^2 ))/t)∣+c  = ln ∣1−(√(1−t^2 )) ∣−ln ∣t∣+c .
lett=sinθcosθdθsinθcosθ=cosecθdθ=lncosecθcotθ+c=ln1t1t2t+c=ln11t2lnt+c.
Commented by arvinddayama01@gmail.com last updated on 06/Oct/18
thanks
thanks

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