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sy7ar

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## Homework Statement

base of a solid is bounded by y=[itex]\sqrt{x}[/itex], the x-axis, and x=9. each cross-section perpendicular to the x-axis is a semi-circle. find the volume of the solid

## Homework Equations

## The Attempt at a Solution

I found the answer to be 81[itex]\pi[/itex]/16 by the following steps:

A(semicircle)=0.5pir^2=(pi/8)*d^2 (d=diameter), and d=y=sqrt(x), so A=(pi/8)*x

integrate (pi/8)*x from 0 to 9 (pi*9^2 /16), I get the answer as 81pi/16

BUT the answer provided by my book is 81pi/8, did I miss something? I'm so confused and please help.

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