Maharashtra BoardEnglish MediumSTD 12 ScienceMathsDefinite Integration2 Marks
MCQ
$\int_0^{100 \pi}|\cos x| d x=$ ________.
✓
200
B
100
C
50
D
$0$
✓
Answer
Correct option: A.
200
(A) Let $I =\int_0^{100 \pi}|\cos x| d x$ $=200 \int_0^{\frac{\pi}{2}}|\cos x| d x$ $\ldots\left[\because \int_0^{2 a } f (x) d x=2 \int_0^{ a } f (x) d x\right.$, if $\left.f (2 a -x)= f (x)\right]$ Since $\cos x$ is positive in the interval $\left(0, \frac{\pi}{2}\right)$ $\therefore I =200 \int_0^{\frac{\pi}{2}} \cos x d x$ $\begin{array}{l}=200[\sin x]_0^{\frac{\pi}{2}} \\ =200\end{array}$
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