On Monday, May 21, 2012 11:08:02 PM UTC+8, Santanu wrote:
>
> When I use the following code it returns 0.
>
> var('x y')
> def f1(x,y):
> if(x+y < 5):
> return x+y
> else:
> return 0
>
> integral(integral(f1(x,y), x, 0,1), y, 0, 1)
>
>
>
> whereas
>
>
> integral(integral(x+y, x, 0,1), y, 0, 1)
>
> returns 1.
>
> Can any one point out the reason for this discrepancy and how to solve it?
I suspect it happens because the inner integral is evaluated first, with a
*symbolic variable* y. Then, the condition c+y < 5 always fails for any
value c that is input as x to f1(x,y). So, the inner integral always
evaluates to 0, and then the outer integral too evaluates to 0.
Unfortunately, I don't know any workarounds to this.
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