Re: Accuracy and Precision

*To*: mathgroup at smc.vnet.net*Subject*: [mg36903] Re: Accuracy and Precision*From*: pkosta2002 at yahoo.com (Peter Kosta)*Date*: Tue, 1 Oct 2002 04:45:51 -0400 (EDT)*References*: <an8stl$6tq$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Thanks to all who adviced me on the correct use of SetAccuracy. However, I still don't understand why the order in which we set the accuracies for f, a, and b matters. In[1]:= f = SetAccuracy[333.75*b^6 + a^2*(11*a^2*b^2 - b^6 - 121*b^4 - 2) + 5.5*b^8 + a/(2*b), Infinity]; a = SetAccuracy[77617., Infinity]; b = SetAccuracy[33096., Infinity]; In[4]:= f Out[4]= -(54767/66192) In[5]:= f = SetAccuracy[333.75*b^6 + a^2*(11*a^2*b^2 - b^6 - 121*b^4 - 2) + 5.5*b^8 + a/(2*b), Infinity] Out[5]= 1180591620717411303424 Similarily: In[1]:= f = SetAccuracy[333.75*b^6 + a^2*(11*a^2*b^2 - b^6 - 121*b^4 - 2) + 5.5*b^8 + a/(2*b), 50]; a = SetAccuracy[77617., 100]; b = SetAccuracy[33096., 100]; In[4]:= f Out[4]= -0.8273960599468212641107299556`11.4133 In[5]:= f = SetAccuracy[333.75*b^6 + a^2*(11*a^2*b^2 - b^6 - 121*b^4 - 2) + 5.5*b^8 + a/(2*b), 100]; Out[5]= 1.180591620717411303424`121.0721*^21 -PK