Volume of a triangle type shape with a square bottom

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Discussion Overview

The discussion revolves around finding the volume of a three-dimensional shape with a square base in the xy-plane, where \(0 \leq x, y \leq 1\). The shape is not classified as a standard prism or pyramid, leading to questions about the appropriate method for volume calculation.

Discussion Character

  • Mathematical reasoning, Technical explanation, Homework-related

Main Points Raised

  • One participant asks how to find the volume of a shape that has a square base but does not fit the definitions of a prism or pyramid.
  • Another participant describes the shape as having a cubic portion for \(0 \leq z \leq 1\) and a triangular portion for \(1 \leq z \leq 2\), proposing a volume calculation method using slicing, resulting in \(V = 1 + \frac{1}{2}\int_0^1 x\,dx = \frac{5}{4}\).
  • A follow-up question seeks clarification on the derivation of the volume formula, specifically whether the "1" represents the volume of the cube or part of the triangular shape.
  • A participant confirms that the "1" is indeed the volume of the cubic portion and provides a formula for the volume of a slice, \(dV = \frac{1}{2}bh\,dx\), where the base is constant and the height varies, leading to the same volume calculation.

Areas of Agreement / Disagreement

Participants generally agree on the interpretation of the shape and the method of volume calculation, but there are questions about specific details of the derivation and the components of the volume formula.

Contextual Notes

The discussion includes assumptions about the shape's geometry and the integration limits, which may not be explicitly stated. The derivation steps and reasoning behind the volume calculation are not fully resolved, leaving some uncertainty in the approach.

Dustinsfl
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How do I find the volume of this shape? The bottom is a square in the xy plane where \(0\leq x,y\leq 1\).

The object isn't a prism or pyramid so I am not sure what to do.

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If I am interpreting this correctly, for $0\le z\le1$ you have a cube whose sieds are 1 unit in length, and for $1\le z\le2$ you have a solid whose cross-sections perpendicular to either the $x$ or $y$ axes are right triangles whose bases are 1 unit in length and altitudes vary linearly from 0 to 1, and so the volume by slicing is:

$$V=1+\frac{1}{2}\int_0^1 x\,dx=\frac{5}{4}$$
 
MarkFL said:
If I am interpreting this correctly, for $0\le z\le1$ you have a cube whose sieds are 1 unit in length, and for $1\le z\le2$ you have a solid whose cross-sections perpendicular to either the $x$ or $y$ axes are right triangles whose bases are 1 unit in length and altitudes vary linearly from 0 to 1, and so the volume by slicing is:

$$V=1+\frac{1}{2}\int_0^1 x\,dx=\frac{5}{4}$$

How did you derive this formula? Is the 1 the volume of the cube or is that part of the triangular shape?
 
Yes the 1 is the volume of the cubical portion of the solid, and for the upper part, the volume of a particular slice is:

$$dV=\frac{1}{2}bh\,dx$$

where the base is a constant 1 and the height is $x$, hence:

$$dV=\frac{1}{2}x\,dx$$

and so summing the slices (and adding in the cubical portion), we find:

$$V=1+\frac{1}{2}\int_0^1 x\,dx$$
 

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