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MathGroup Archive 2000

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Re: Annoying Little Problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg24739] Re: [mg24701] Annoying Little Problem
  • From: BobHanlon at aol.com
  • Date: Wed, 9 Aug 2000 02:31:42 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 8/4/2000 1:30:31 AM, ayrton at rac1.wam.umd.edu writes:

>I'm having an annoying little problem with version 4.0.1.0. I wrote the
>
>following info in a notebook and ran it:
>
>Clear[v2]
>v2 = {4, 0, -6}
>N[Sqrt[v2.v2]]
>N[Sqrt[v2.v2], 3]
>
>Now the third line gives me 7.2111 but the fourth line gives me the 
>same instead of 7.21. Does anyone have any idea what may be the problem?
>
>Am I doing something wrong?
>

?N

"N[expr] gives the numerical value of expr. N[expr, n] attempts to give a \
result with n-digit precision."

Note that while this indicates the precision of the result, it does not say 
anything about how the result is printed.

Clear[v2]; v2 = {4, 0, -6};

Table[NumberForm[N[Sqrt[v2.v2]], k], {k, 7}]

{"7.", "7.2", "7.21", "7.211", "7.2111", "7.2111", "7.211103"}

Note that for k=5 and k=6 the display is the same, i.e., the trailing zero is 
suppressed for k=6. To display the trailing zero

Table[NumberForm[N[Sqrt[v2.v2]], {k, k - 1}, NumberPadding -> {"", "0"}], {k, 
    7}]

{"7.", "7.2", "7.21", "7.211", "7.2111", "7.21110", "7.211103"}


Bob Hanlon


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