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The area enclosed between the curves |x|...

The area enclosed between the curves `|x| + |y| ge 2 and y ^(2) =4 (1- (x ^(2))/(9))` is :

A

`(6pi -4 )` sq. units

B

`(6pi -8)` se. units

C

`(3pi-4)` se. units

D

`(3pi-2)` sq. units

Text Solution

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The correct Answer is:
To find the area enclosed between the curves \( |x| + |y| \geq 2 \) and \( y^2 = 4(1 - \frac{x^2}{9}) \), we will follow these steps: ### Step 1: Understand the curves The first curve \( |x| + |y| = 2 \) represents a diamond shape (or square rotated by 45 degrees) with vertices at (2,0), (0,2), (-2,0), and (0,-2). The second curve \( y^2 = 4(1 - \frac{x^2}{9}) \) is an ellipse centered at the origin with semi-major axis 2 (along the y-axis) and semi-minor axis 3 (along the x-axis). ### Step 2: Determine the intersection points To find the area enclosed between the curves, we first need to find the points where they intersect. We can substitute \( y \) from the ellipse equation into the diamond equation. From the ellipse equation: \[ y = \pm 2\sqrt{1 - \frac{x^2}{9}} \] Substituting into the diamond equation \( |x| + |y| = 2 \): \[ |x| + 2\sqrt{1 - \frac{x^2}{9}} = 2 \] ### Step 3: Solve for \( x \) We can solve for \( x \) by isolating the square root: \[ 2\sqrt{1 - \frac{x^2}{9}} = 2 - |x| \] \[ \sqrt{1 - \frac{x^2}{9}} = 1 - \frac{|x|}{2} \] Squaring both sides: \[ 1 - \frac{x^2}{9} = \left(1 - \frac{|x|}{2}\right)^2 \] Expanding the right side: \[ 1 - \frac{x^2}{9} = 1 - |x| + \frac{x^2}{4} \] ### Step 4: Rearranging the equation Rearranging gives: \[ -\frac{x^2}{9} + |x| - \frac{x^2}{4} = 0 \] Multiplying through by 36 to eliminate the fractions: \[ -4x^2 + 36|x| - 9x^2 = 0 \] Combining like terms: \[ -13x^2 + 36|x| = 0 \] ### Step 5: Factor the equation Factoring out \( |x| \): \[ |x|(36 - 13|x|) = 0 \] This gives us \( |x| = 0 \) or \( |x| = \frac{36}{13} \). ### Step 6: Find corresponding \( y \) values For \( |x| = 0 \): \[ y = \pm 2 \] For \( |x| = \frac{36}{13} \): Substituting back into the ellipse equation: \[ y^2 = 4\left(1 - \frac{(\frac{36}{13})^2}{9}\right) \] Calculating gives the corresponding \( y \) values. ### Step 7: Set up the double integral The area \( A \) can be calculated using a double integral: \[ A = 4 \int_0^2 \left(3\sqrt{4 - y^2} - (2 - y)\right) dy \] ### Step 8: Evaluate the integral Calculating the integral: 1. Solve \( \int_0^2 3\sqrt{4 - y^2} dy \) using the formula for the area of a quarter circle. 2. Solve \( \int_0^2 (2 - y) dy \). ### Step 9: Combine results Combine the results from the integrals to find the total area. ### Final Answer The area enclosed between the curves is \( 6\pi - 8 \) square units. ---
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