
Derive and disk volume method
Posted:
Apr 6, 1998 11:35 AM


I spent the morning figuring out how to draw a rotated 2D 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 xaxis 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

