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The base of a solid is the region enclosed by the graphs of 
y=sin(x) and 
y=4-sqrtx, between 
x=2 and 
x=7.
Cross sections of the solid perpendicular to the 
x-axis are rectangles whose height is 
2x.
Which one of the definite integrals gives the volume of the solid?
Choose 1 answer:
(A) 
int_(2)^(7)[(4-sqrtx)^(2)-sin^(2)(x)]dx
(B) 
int_(2)^(7)[sin(x)+sqrtx-4]*2xdx
(C) 
int_(2)^(7)[sin^(2)(x)-(4-sqrtx)^(2)]dx
(D) 
int_(2)^(7)[4-sqrtx-sin(x)]*2xdx

The base of a solid is the region enclosed by the graphs of y=sin(x) y=\sin (x) and y=4x y=4-\sqrt{x} , between x=2 x=2 and x=7 x=7 .\newlineCross sections of the solid perpendicular to the x x -axis are rectangles whose height is 2x 2 x .\newlineWhich one of the definite integrals gives the volume of the solid?\newlineChoose 11 answer:\newline(A) 27[(4x)2sin2(x)]dx \int_{2}^{7}\left[(4-\sqrt{x})^{2}-\sin ^{2}(x)\right] d x \newline(B) 27[sin(x)+x4]2xdx \int_{2}^{7}[\sin (x)+\sqrt{x}-4] \cdot 2 x d x \newline(C) 27[sin2(x)(4x)2]dx \int_{2}^{7}\left[\sin ^{2}(x)-(4-\sqrt{x})^{2}\right] d x \newline(D) 27[4xsin(x)]2xdx \int_{2}^{7}[4-\sqrt{x}-\sin (x)] \cdot 2 x d x

Full solution

Q. The base of a solid is the region enclosed by the graphs of y=sin(x) y=\sin (x) and y=4x y=4-\sqrt{x} , between x=2 x=2 and x=7 x=7 .\newlineCross sections of the solid perpendicular to the x x -axis are rectangles whose height is 2x 2 x .\newlineWhich one of the definite integrals gives the volume of the solid?\newlineChoose 11 answer:\newline(A) 27[(4x)2sin2(x)]dx \int_{2}^{7}\left[(4-\sqrt{x})^{2}-\sin ^{2}(x)\right] d x \newline(B) 27[sin(x)+x4]2xdx \int_{2}^{7}[\sin (x)+\sqrt{x}-4] \cdot 2 x d x \newline(C) 27[sin2(x)(4x)2]dx \int_{2}^{7}\left[\sin ^{2}(x)-(4-\sqrt{x})^{2}\right] d x \newline(D) 27[4xsin(x)]2xdx \int_{2}^{7}[4-\sqrt{x}-\sin (x)] \cdot 2 x d x
  1. Integrate Area of Cross Sections: To find the volume of the solid, we need to integrate the area of the cross sections along the xx-axis from x=2x=2 to x=7x=7. The area of each rectangular cross section is given by the difference in the yy-values of the two functions (the height of the rectangle) times the given height of the rectangle (2x2x). The correct integral will have the form [f(x)g(x)]h(x)dx\int [f(x) - g(x)] \cdot h(x) \, dx, where f(x)f(x) and g(x)g(x) are the yy-values of the top and bottom functions, respectively, and h(x)h(x) is the height of the rectangle.
  2. Determine Top Function: First, we need to determine which function is on top (has a larger yy-value) between x=2x=2 and x=7x=7. Since y=4xy=4-\sqrt{x} is a decreasing function and y=sin(x)y=\sin(x) oscillates between 1-1 and 11, y=4xy=4-\sqrt{x} will be on top for the entire interval from x=2x=2 to x=7x=7.
  3. Calculate Cross Section Area: The area of each cross section is therefore (4xsin(x))(4 - \sqrt{x} - \sin(x)) times the height of the rectangle, which is 2x2x. This gives us the integrand (4xsin(x))×2x(4 - \sqrt{x} - \sin(x)) \times 2x.
  4. Find Correct Integral: The correct integral for the volume of the solid is therefore x=2x=7(4xsin(x))2xdx\int_{x=2}^{x=7} (4 - \sqrt{x} - \sin(x)) \cdot 2x \, dx. This matches option (D).

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