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Let g (x) =x ^(2),f (x) = sqrtx, and alp...

Let `g (x) =x ^(2),f (x) = sqrtx, and alpha, beta ( alpha lt beta)` be the roots of the quadratic equation `18 x ^(2) - 9pix + pi^(2) =0.` Then the area (is sq. units) bounded by curve `y = (gof) (x)` and the lines `x =alpha, x = betaand y =0` is :

A

`(pi^2)/24`

B

`(pi^2)/9`

C

`(pi^2)/36`

D

`(pi^2)/72`

Text Solution

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The correct Answer is:
To solve the problem, we need to find the area bounded by the curve \( y = (g \circ f)(x) \), the lines \( x = \alpha \), \( x = \beta \), and \( y = 0 \). Let's break down the solution step by step. ### Step 1: Define the Functions We are given: - \( g(x) = x^2 \) - \( f(x) = \sqrt{x} \) ### Step 2: Find the Composition of Functions We need to find \( g(f(x)) \): \[ g(f(x)) = g(\sqrt{x}) = (\sqrt{x})^2 = x \] Thus, the curve is represented by the equation \( y = x \). ### Step 3: Identify the Roots of the Quadratic Equation We need to find the roots of the quadratic equation: \[ 18x^2 - 9\pi x + \pi^2 = 0 \] Using the quadratic formula \( x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \): - Here, \( a = 18 \), \( b = -9\pi \), and \( c = \pi^2 \). Calculating the discriminant: \[ b^2 - 4ac = (-9\pi)^2 - 4 \cdot 18 \cdot \pi^2 = 81\pi^2 - 72\pi^2 = 9\pi^2 \] Now, applying the quadratic formula: \[ x = \frac{9\pi \pm 3\pi}{36} \] This gives us two roots: \[ x_1 = \frac{12\pi}{36} = \frac{\pi}{3}, \quad x_2 = \frac{6\pi}{36} = \frac{\pi}{6} \] Thus, we have: \[ \alpha = \frac{\pi}{6}, \quad \beta = \frac{\pi}{3} \] ### Step 4: Set Up the Integral for Area Calculation The area \( A \) bounded by the curve \( y = x \) and the lines \( x = \alpha \), \( x = \beta \), and \( y = 0 \) can be calculated using the integral: \[ A = \int_{\alpha}^{\beta} x \, dx = \int_{\frac{\pi}{6}}^{\frac{\pi}{3}} x \, dx \] ### Step 5: Compute the Integral Calculating the integral: \[ A = \left[ \frac{x^2}{2} \right]_{\frac{\pi}{6}}^{\frac{\pi}{3}} = \frac{1}{2} \left( \left(\frac{\pi}{3}\right)^2 - \left(\frac{\pi}{6}\right)^2 \right) \] Calculating each term: \[ \left(\frac{\pi}{3}\right)^2 = \frac{\pi^2}{9}, \quad \left(\frac{\pi}{6}\right)^2 = \frac{\pi^2}{36} \] Now substituting back: \[ A = \frac{1}{2} \left( \frac{\pi^2}{9} - \frac{\pi^2}{36} \right) \] Finding a common denominator (36): \[ \frac{\pi^2}{9} = \frac{4\pi^2}{36} \] Thus: \[ A = \frac{1}{2} \left( \frac{4\pi^2}{36} - \frac{\pi^2}{36} \right) = \frac{1}{2} \left( \frac{3\pi^2}{36} \right) = \frac{3\pi^2}{72} = \frac{\pi^2}{24} \] ### Final Result The area bounded by the curve and the lines is: \[ \boxed{\frac{\pi^2}{24}} \text{ square units} \]
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