If x=1 and ∑(x5+x4+3x3+3x2+x+1)tan−1(xx2+1)(x3+x2−x−1)dx =Alog(f(x))+C,thenA−tan(f(2))=
Topic: JEE PYQ
Answer: A. Full step-by-step solution below.
A2−3
B2−1
C27
D-2
Correct answer: A
Solution
(a) Let I=∑(x5+x4+3x3+3x2+x+1)tan−1(xx2+1)x3+x2−x−1dxasx=1 =∫(x(x4+3x2+1)+(x4+3x2+1))tan−1(xx2+1)x(x2−1)+x2−1dx=∫(x4+3x2+1)(x+1)tan−1(xx2+1)(x+1)(x2−1)dx=∫(x4+3x2+1)tan−1(xx2+1)x2−1dxLettan−1(xx2+1)=t(∵dxdtan−1(x)=1+x21) ⇒1+(xx2+1)21⋅x22x(x)−(x2+1)dx=dt⇒x4+3x2+1x2−1dx=dt⇒I=∫t1dt=logt+C=logtan−1(xx2+1)+C∴A=1,f(x)=tan−1(xx2+1)∴A−tanf(2)=1−tantan−125=1−25=−23