Calc 2 solids of revolution help

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Homework Help Overview

The discussion revolves around a calculus problem involving solids of revolution, specifically focusing on finding the area of cross-sections of a solid defined between two planes. The problem specifies semicircular boundaries and equilateral triangular cross-sections, with a particular emphasis on the case where a=7.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to derive a formula for the area of the cross-section at a given location x, using geometric properties of equilateral triangles and semicircles. They express uncertainty about their calculations, particularly regarding the height of the triangle.

Discussion Status

The discussion is ongoing, with participants providing feedback on the original poster's reasoning. Some participants have pointed out potential mistakes in the calculations, specifically concerning the height of the triangle, while the original poster seeks clarification on why their answer is deemed incorrect.

Contextual Notes

The problem is part of an online homework assignment, which may impose specific constraints or requirements that are not fully detailed in the discussion.

kellyb1ll
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A solid lies between planes perpendicular to the x-axis at x=-a and x=a for values of a>0 to be given below in parts (i) and (ii). In each case the cross-sections perpendicular to the x-axis between these planes run from the semicircle y=√(a^2-x^2) to the semicircle
y=-√(a^2-x^2).

If a=7 and the cross-sections are equilateral triangles with bases in the x-y plane, find a formula for the area A(x) of the cross-section at location x.


For the base i used 2*√(a^2-x^2), for the height i used √(a^2-x^2)/tan(30). so i get
(a^2-x^2)/tan(30) as an answer, which is not right. what am i doing wrong i can't seem to figure it out.

i uploaded a picture of what the problem gave me if it helps.
THANKS!
 

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Why do you think that is not right?
 
its a problem on my online homework and when i type in that answer it says its wrong
 
You made a mistake finding the height of the triangle.
 

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