Match List-I with List-II
| List-I | List-II | ||
|---|---|---|---|
| (A) | \(\int_{-a}^{a}\displaystyle f(x)\,dx = 0\) | (I) | 0 |
| (B) | \(\int_{0}^{2a}\displaystyle f(x)\,dx = 2\int_{0}^{a} f(x)\,dx\) | (II) | 1 |
| (C) | \(\int_{-\pi}^{\pi}\displaystyle \cos x\,dx\) | (III) | \(f\) is an odd function |
| (D) | \(\int_{-1}^{1}\displaystyle x^{101}\,dx + 1\) | (IV) | \(f(2a - x) = f(x)\) |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A)-(III), (B)-(IV), (C)-(I), (D)-(II)
(A) \(\int_{-a}^{a} f(x)\,dx = 0\)
This matches (III) f is an odd function. Splitting the integral at 0:
\(\displaystyle \int_{-a}^{a} f(x)\,dx = \int_{-a}^{0} f(x)\,dx + \int_{0}^{a} f(x)\,dx\)
Putting x = −t in the first integral, and using f(−t) = −f(t) for an odd function:
\(\displaystyle \int_{-a}^{0} f(x)\,dx = \int_{0}^{a} f(-t)\,dt = -\int_{0}^{a} f(t)\,dt\)
So the two parts cancel and the integral is 0.
(B) \(\int_{0}^{2a} f(x)\,dx = 2\int_{0}^{a} f(x)\,dx\)
This matches (IV) \(f(2a - x) = f(x)\). Splitting the integral at a:
\(\displaystyle \int_{0}^{2a} f(x)\,dx = \int_{0}^{a} f(x)\,dx + \int_{a}^{2a} f(x)\,dx\)
Putting x = 2a − t in the second integral:
\(\displaystyle \int_{a}^{2a} f(x)\,dx = \int_{0}^{a} f(2a - t)\,dt = \int_{0}^{a} f(t)\,dt\)
So the two parts are equal and the integral is \(2\int_{0}^{a} f(x)\,dx\).
(C) \(\int_{-\pi}^{\pi} \cos x\,dx\)
This matches (I) 0:
\(\displaystyle \int_{-\pi}^{\pi} \cos x\,dx = \Big[\sin x\Big]_{-\pi}^{\pi} = 0 - 0 = 0\)
(D) \(\int_{-1}^{1} x^{101}\,dx + 1\)
This matches (II) 1. Since \(x^{101}\) is an odd function, its integral over [−1, 1] is 0 by (A):
\(\displaystyle \int_{-1}^{1} x^{101}\,dx + 1 = 0 + 1 = 1\)
So the matching is (A)-(III), (B)-(IV), (C)-(I), (D)-(II).