BITSAT 2009
- Exam
- BITSAT
- Year
- 2009
- Subject
- Mathematics
- Chapter
- Indefinite Integration
BITSAT 2009 · Mathematics · Indefinite Integration
If ( ∫ (2 x- x+λ)/( x+ x-2) d x) (=A | x+ x-2|+B x+C). Then the...
If (d x) (=A \ln |\cos x+\sin x-2|+B x+C).
Then the ordered triplet (A, B, \lambda) is -
Options
- A(\left(\frac{1}{2}, \frac{3}{2},-1\right))
- B(\left(\frac{3}{2}, \frac{1}{2},-1\right))
- C(\left(\frac{1}{2},-1, \frac{3}{2}\right))
- D(\left(\frac{3}{2},-1, \frac{1}{2}\right))
Correct answer
B. (\left(\frac{3}{2}, \frac{1}{2},-1\right))
Step-by-step solution
$\begin{aligned} \frac{\mathrm{d}}{\mathrm{dx}}(\mathrm{A} \ln |\cos \mathrm{x}+\sin \mathrm{x}-2|+\mathrm{Bx}+\mathrm{C})\\
&= \mathrm{A} \frac{\cos \mathrm{x}-\sin \mathrm{x}}{\cos \mathrm{x}+\sin \mathrm{x}-2}+\mathrm{B}\\
&= \frac{\mathrm{A} \cos \mathrm{x}-\mathrm{A} \sin \mathrm{x}+\mathrm{B} \cos \mathrm{x}+\mathrm{B} \sin \mathrm{x}-2 \mathrm{ B}}{\cos \mathrm{x}+\sin \mathrm{x}-2}\\
& \therefore 2=\mathrm{A}+\mathrm{B} \text{ or }-1=-\mathrm{A}+\mathrm{B}; \lambda=-2 \mathrm{ B}\\
& \therefore \mathrm{A}=3 / 2, \mathrm{ B}=1 / 2, \lambda=-1
\end{aligned}$)