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 Author Comment/Response Doug VanGoethem 11/16/00 4:46pm Hello all, I am trying to do mechanics calculations for composite thin walled tubes. It seems natural to use polar coordinates to enable generality. This way a single function r[theta] can be used (vs. something like f_top[x] & f_btm[x]) and vertical lines in the cross section are not a problem. I have successfully done all of the calculations using a circular cross section. Now I want to examine a rectangular section. Naturally this will be defined as a piecewise function of theta. At first I tried defining this function with a Which statement. This will give a function that looks correct when plotted, but will not behave correctly in the ensuing integrations. Then I defined the piecewise function numerically as follows: Step[x_,l_,u_]=UnitStep[x-l]-UnitStep[x-u]; r[th] = r1[th]*Step[theta,a,b] + r2[th]*Step[theta,b,c] + .......etc (where r1[th] is a horizontal line defining the top of the box, r2[th] is a vertical line defining the left side, etc) This should have worked swimmingly, but I get an Indeterminate result at 0, pi/2, pi, 3pi/2, and 2pi. For example at pi/2 only r1[th] should be contributing, but r2[th] and r4[th] return ComplexInfinity at that value and Mathematica doesn't know what to do with 0*Infinity. Does anyone have any suggestions for fixing this? Is there some way to temporarily define 0*Infinity as 0? Or is there any other way to get the noncontributing functions to go to zero over a given interval? Thanks in advance, Doug -- Doug VanGoethem Composite Materials, Manufacture, and Structures Lab Colorado State University email: vango@lamar.colostate.edu phone: (970)491-8678 fax: (970)491-8671 URL: ,

 Subject (listing for 'difficult piecwise continuous function') Author Date Posted difficult piecwise continuous function Doug VanGoet... 11/16/00 4:46pm Re: difficult piecwise continuous function Forum Modera... 11/21/00 10:43am
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