       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:=
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:=
f

Out=
-(54767/66192)

In:=
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=
1180591620717411303424

Similarily:

In:=
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:=
f

Out=
-0.8273960599468212641107299556`11.4133

In:=
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=
1.180591620717411303424`121.0721*^21

-PK

```

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