MCQ
Let $f(x)$ be a function satisfying $f(x)+f(\pi-x)=$ $\pi^2, \forall x \in R$. Then $\int \limits_0^\pi f(x) \sin x d x$ is equal to $...........$.
- A$\frac{\pi^2}{4}$
- B$\frac{\pi^2}{2}$
- C$2 \pi^2$
- ✓$\pi^2$
$I=\int \limits_0^\pi f(x) \sin x d x$
Applying King's Rule
$I=\int \limits_0^\pi f(\pi-x) \cdot \sin (\pi-x) d x$
$2 I=\int \limits_0^\pi[f(x)+f(\pi-x)] \sin x d x$
$2 I=\int \limits_0^\pi \pi^2 \sin x d x$
$2 I=\pi^2 \cdot \int \limits_0^\pi \sin x d x$
$2 I=\pi^2 \times 2$
$I=\pi^2$
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$(A)$: $\max \left\{\left|a_1\right|,\left|a_2\right|,\left|a_3\right|\right\} \leq|\vec{a}|$
$(B)$: $|\vec{a}| \leq 3 \max \left\{\left| a _1\right|,\left| a _2\right|,\left| a _3\right|\right\}$