|
|
| Line 1: |
Line 1: |
| [[File:Disc integration.svg|thumb|right|170px]]
| | These products call me Gabrielle. Vermont has always been my staying place and I enjoy everything that I would need here. As a girl what I definitely like is going within order to karaoke but I do not have made a dime going without running shoes. I am a particular cashier and I'm accomplishing pretty good [http://en.Search.wordpress.com/?q=financially financially]. See what's new on my own, personal website here: http://prometeu.net<br><br>My page :: [http://prometeu.net clash of clans cheats] |
| {{Calculus |Integral}}
| |
| | |
| '''Disk integration''', also known in [[integral calculus]] as the '''disk method''', is a means of calculating the [[volume]] of a [[solid of revolution]] of a solid-state material when [[Integral|integrating]] along the [[axis of revolution]]. This method models the resulting three-dimensional shape as a "stack" of an infinite number of disks of varying radius and infinitesimal thickness. It is also possible to use the same principles with "washers" instead of "disks" (the "'''washer method'''") to obtain "hollow" solids of revolutions.
| |
| | |
| == Definition ==
| |
| | |
| ===Function of ''x''===
| |
| If the function to be revolved is a function of <math>x</math>, the following integral represents the volume of the solid of revolution:
| |
| | |
| : <math>\pi \int_a^b [R(x)]^2\ \mathrm{d}x</math>
| |
| | |
| where <math>R(x)</math> is the distance between the function and the axis of rotation. This works only if the [[axis of rotation]] is horizontal (example: <math>y=3</math> or some other constant).
| |
| | |
| ===Function of ''y''===
| |
| If the function to be revolved is a function of <math>y</math>, the following integral will obtain the volume of the solid of revolution:
| |
| | |
| : <math>\pi \int_c^d [R(y)]^2\ \mathrm{d}y</math>
| |
| | |
| where <math>R(y)</math> is the distance between the function and the axis of rotation. This works only if the [[axis of rotation]] is vertical (example: <math>x=4</math> or some other constant).
| |
| | |
| ===Washer method===
| |
| To obtain a "hollow" solid of revolution (the "washer method"), the procedure would be to take the volume of the inner solid of revolution and subtract it from the volume of the outer solid of revolution. This can be calculated in a single integral similar to the following:
| |
| | |
| : <math>\pi \int_a^b (\left[R_O(x)\right]^2 - \left[R_I(x)\right]^2) \mathrm{d}x</math>
| |
| | |
| where <math>R_O(x)</math> is the function that is farthest from the axis of rotation and <math>R_I(x)</math> is the function that is closest to the axis of rotation. One should take caution not to evaluate the square of the difference of the two functions, but to evaluate the difference of the squares of the two functions.
| |
| | |
| : <math> [R_O(x)]^2 - [R_I(x)]^2\ \not\equiv \; [R_O(x) - R_I(x)]^2</math>
| |
| | |
| ''The above formula only works for revolutions about the x-axis.''
| |
| | |
| To rotate about any horizontal axis, simply subtract from that axis each formula:
| |
| | |
| if <math>h</math> is the value of a horizontal axis, then the volume =
| |
| | |
| : <math>\pi \int_a^b ([h-R_O(x)]^2 - [h-R_I(x)]^2)\, \mathrm{d}x.</math> | |
| | |
| For example, to rotate the region between <math> y=-2x+x^2 </math> and <math> y=x </math>
| |
| | |
| along the axis <math>y=4</math>, one would integrate as follows:
| |
| | |
| : <math>\pi \int_0^3 ([4-(-2x+x^2)]^2 - [4-x]^2)\, \mathrm{d}x.</math> | |
| | |
| The bounds of integration are the zeros of the first equation minus the second. Note that when you integrate along an axis other than the <math>x</math>, the further axis may not be that obvious. In the previous example, even though <math>y=x</math> is further up than <math> y=-2x+x^2 </math>, it is the inner axis since it is closer to <math>y=4</math>
| |
| | |
| The same idea can be applied to both the y-axis and any other vertical axis. You simply must solve each equation for <math>x</math> before you insert them into the integration formula.
| |
| | |
| == See also ==
| |
| * [[Solid of revolution]]
| |
| * [[Shell integration]]
| |
| | |
| ==References==
| |
| {{Refbegin|normalfont=yes}}
| |
| *{{cite web|title=Volumes of Solids of Revolution|url=http://www.cliffsnotes.com/study_guide/topicArticleId-39909,articleId-39907.html|work=CliffsNotes.com|accessdate=July 12, 2013}}
| |
| *{{MathWorld|title=Method of Disks|urlname=MethodofDisks}} {{accessdate|July 12, 2013}}
| |
| *Frank Ayres, Elliott Mendelson. ''Schaum's outlines: Calculus''. McGraw-Hill Professional 2008, ISBN 978-0-07-150861-2. pp. 244–248 ({{Google books|Ag26M8TII6oC|online copy|page=244}}{{accessdate|July 12, 2013}})
| |
| {{Refend}}
| |
| | |
| | |
| [[Category:Integral calculus]]
| |
| [[Category:Volume]]
| |
These products call me Gabrielle. Vermont has always been my staying place and I enjoy everything that I would need here. As a girl what I definitely like is going within order to karaoke but I do not have made a dime going without running shoes. I am a particular cashier and I'm accomplishing pretty good financially. See what's new on my own, personal website here: http://prometeu.net
My page :: clash of clans cheats