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Statement-1: int(0)^(pi//2) x cot x dx=(...

Statement-1: `int_(0)^(pi//2) x cot x dx=(pi)/(2)log2`
Statement-2: `int_(0)^(pi//2) log sin x dx=-(pi)/(2)log2`

A

Statement-1 is true, Statement-2 is True,Statement-2 is a correct explanation for Statement-1.

B

Statement-1 is True, Statement-2 is not a correct explanation for Statement-1.

C

Statement-1 is True, Statement-2 is False.

D

Statement-1 is False, Statement-2 is True.

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to evaluate the two statements regarding definite integrals. ### Statement 1: We need to evaluate the integral: \[ I_1 = \int_{0}^{\frac{\pi}{2}} x \cot x \, dx \] ### Step 1: Integration by Parts We can use integration by parts, where we let: - \( u = x \) → \( du = dx \) - \( dv = \cot x \, dx \) → \( v = \log(\sin x) \) Using the integration by parts formula: \[ \int u \, dv = uv - \int v \, du \] we have: \[ I_1 = x \log(\sin x) \bigg|_{0}^{\frac{\pi}{2}} - \int_{0}^{\frac{\pi}{2}} \log(\sin x) \, dx \] ### Step 2: Evaluate the Boundary Terms Now, we evaluate the boundary terms \( x \log(\sin x) \) at \( x = \frac{\pi}{2} \) and \( x = 0 \): - At \( x = \frac{\pi}{2} \): \[ \frac{\pi}{2} \log(\sin(\frac{\pi}{2})) = \frac{\pi}{2} \log(1) = 0 \] - At \( x = 0 \): \[ \lim_{x \to 0} x \log(\sin x) \] Using L'Hôpital's rule, we can rewrite this as: \[ \lim_{x \to 0} x \log(x) = \lim_{x \to 0} \frac{\log(x)}{1/x} \] Differentiating the numerator and denominator: \[ = \lim_{x \to 0} \frac{1/x}{-1/x^2} = \lim_{x \to 0} -x = 0 \] Thus, the boundary terms evaluate to: \[ 0 - 0 = 0 \] ### Step 3: Substitute Back Now substituting back into the integral: \[ I_1 = 0 - \int_{0}^{\frac{\pi}{2}} \log(\sin x) \, dx \] Thus, we have: \[ I_1 = -\int_{0}^{\frac{\pi}{2}} \log(\sin x) \, dx \] ### Step 4: Using Statement 2 From Statement 2, we know: \[ \int_{0}^{\frac{\pi}{2}} \log(\sin x) \, dx = -\frac{\pi}{2} \log 2 \] Substituting this into our expression for \( I_1 \): \[ I_1 = -\left(-\frac{\pi}{2} \log 2\right) = \frac{\pi}{2} \log 2 \] ### Conclusion for Statement 1 Thus, we conclude that: \[ \int_{0}^{\frac{\pi}{2}} x \cot x \, dx = \frac{\pi}{2} \log 2 \] This confirms that Statement 1 is true. ### Summary for Statement 2 We have: \[ \int_{0}^{\frac{\pi}{2}} \log(\sin x) \, dx = -\frac{\pi}{2} \log 2 \] This confirms that Statement 2 is also true. ### Final Answer Both statements are true: - Statement 1: True - Statement 2: True

To solve the problem, we need to evaluate the two statements regarding definite integrals. ### Statement 1: We need to evaluate the integral: \[ I_1 = \int_{0}^{\frac{\pi}{2}} x \cot x \, dx \] ...
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Knowledge Check

  • int_(0)^(pi//2)log (sec x) dx=

    A
    `(-pi)/2log2`
    B
    `pi/2 log 2`
    C
    `(-pi)/4 log 2`
    D
    `pi/4log2`
  • int_(0)^(pi//2) log (tan x ) dx=

    A
    0
    B
    `pi`
    C
    `pi/2`
    D
    `pi/4`
  • int_(0)^(pi)log sin^(2)x dx=

    A
    `2pilog_(e)(1/2)`
    B
    `pi log_(e)2`
    C
    `(pi)/2log_(e)(1/2)`
    D
    `pilog_(e)(1/2)`
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