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#822 sinh(bigfloat) not accurate

closed
nobody
Lisp Core (472)
5
2006-01-06
2005-11-30
Raymond Toy
No

sinh for small bigfloats is not very accurate:

(%i14) display2d:false;
(%o14) false
(%i15) fpprec:20;
(%o15) 20
(%i16) sinh(1b-8);
(%o16) 9.9999999999999042563B-9
(%i17) x+x^3/3!+x^5/5!;
(%o17) x^5/120+x^3/6+x
(%i18) ev(%,x=1b-8);
(%o18) 1.0000000000000000167B-8

Maxima converts sinh to exponential form and computes
the value using that formula, which is not very
accurate for x near 0.

Discussion

  • Raymond Toy
    Raymond Toy
    2006-01-06

    Logged In: YES
    user_id=28849

    Fixed in CVS:

    (%i18) sinh(1b-8);
    (%o18) 1.0000000000000000167b-8

     
  • Raymond Toy
    Raymond Toy
    2006-01-06

    • status: open --> closed