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#2685 radcan too ambitious

None
wont-fix
nobody
radcan (1)
5
2014-02-19
2014-01-30
No

(%i1) radcan(sqrt((5c/6-250/183)^2+(100/61-c)^2));
(%o1) (61
c-100)/(6*sqrt(61))

The result could be negative, but it is a sqrt(...).

(%i2) factor(sqrt((5c/6-250/183)^2+(100/61-c)^2));
(%o2) abs(61
c-100)/(6*sqrt(61))

Here we get the required abs(x) function.

The error appears regardless of the setting of radexpand

Discussion

  • This is actually the expected behaviour of radcan. Unfortunately, its documentation isn't all that brilliant at the moment - I think Raymond Toy has been trying to come up with a more formal specification. He explains what's going on in a similar bug report here: https://sourceforge.net/p/maxima/bugs/2479/

    In this case, the point is that if c is large then 61 * c >> 100.

     
    • labels: --> radcan
    • status: open --> wont-fix