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Topic: Derive and disk volume method
Replies: 2   Last Post: Apr 8, 1998 11:53 AM

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Dave Slomer

Posts: 244
Registered: 12/6/04
Derive and disk volume method
Posted: Apr 6, 1998 11:35 AM
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I spent the morning figuring out how to draw a rotated 2-D region via
Derive.

DISKVOL(f, x, a, b, h, n, dir) :=3D
VECTOR(ISOMETRICS(ROTATE_Y(dir=B7PI/2)=B7CYLINDER(f, theta, z), theta=
, 0, 2=B7PI,
n, z, x, x + h/2, 1), x, a, b - h, h)

You have to load the GRAPHICS.MTH file first.

To rotate the region bounded by y=3Dsin(x) and the x-axis over [1,2] =
using
disks of thickness .1 (each disk created with 12 sides) so that the s=
olid
"recedes into the screen", you'd use:

DISKVOL(SIN(X),X,1,2,.1,12,-1)

Once you've simplified and plotted the solid, you can then change the=
plot
color and plot

DISKVOL(SIN(x), x, 1, 1.1, 0.1, 16,-1)

which would give ONE disk in a different color, located over [1,1.1].

I'd be glad to post this and more to my web site sooner than I had pl=
anned
if encouraged!

I'd also be glad to know if there's an easier way!!

Dave Slomer
AP Calculus and computer science teacher
Winton Woods HS, Cinti, OH 45240
http://www.geocities.com/capecanaveral/lab/8692







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