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Fixed roots() - bug?
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Offline omorr  
#1 Posted : 18 June 2011 22:50:37(UTC)
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Hello,

I can not see why roots() is working wrong with the second guess value.
Could someone reproduce this please, or tell me if I am doing anything wrong.
If you can reproduce - this might be a bug, or something wrong with my computer (WinXp, SMath v0.89.8 Portable).

Regards,
Radovan

Edited by user 15 February 2012 01:16:57(UTC)  | Reason: Not specified

When Sisyphus climbed to the top of a hill, they said: "Wrong boulder!"
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Offline bdrunagle  
#2 Posted : 19 June 2011 00:25:42(UTC)
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Hi Radovan

I've just done a very quick check and I get exactly the same results you show using
Smath 0.89 build 8
Windows 7

I don't know why this should happen, sorry.

Brian
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Offline omorr  
#3 Posted : 19 June 2011 09:21:04(UTC)
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Thank you Brian,

This is a Live version:
Open in SMath Cloud
Hmm...it seems that is definitely a bug.
With another function - it is Ok
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Regards,
Radovan

Edited by user 19 June 2011 09:36:06(UTC)  | Reason: Not specified

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Offline omorr  
#4 Posted : 19 June 2011 09:46:22(UTC)
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Strange? If the 2 in denominator is changed a bit - it is OK???
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Regards,
Radovan
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Offline bliengme  
#5 Posted : 01 October 2011 07:53:06(UTC)
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I am using the beta version and do not get this error. In both cases root = +- 2.83 (with b=1, c=1)
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Offline omorr  
#6 Posted : 01 October 2011 09:22:32(UTC)
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Hello,
bliengme wrote:
I am using the beta version and do not get this error. In both cases root = +- 2.83 (with b=1, c=1)

Take a look at the previous example, please. If you use b=1, c=1 the result is correct, but if you use b=1, c=2 then it is not correct.

f(a,b,c):{a^2-2*b}/{2+c}-2
b:1 c:1
roots(f(x,b,c),x,-10)=-2.8284
roots(f(x,b,c),x,10)=2.8284
b:1 c:2
roots(f(x,b,c),x,-10)=-3.1623
roots(f(x,b,c),x,10)=10@# - WRONG

or

roots(f(x,b,c),x,10000)=10000@#

but if you put something like

f(a,b,c):{a^2-2*b}/{2.0000000000001+c}-2

the result is RIGHT! Moreover, Instead of 2+c in the denominator you can put 4+c, 6+c -4+c or any other even number instead of 2 and there will be wrong again. If you put any odd integer (positive , negative) or a real number, the result will be right.There must be some bug here.

roots(f(x,b,c),x,10000)=3.1623@#

On the other hand

solve(f(x,b,c),x,-100,100)=mat(-3.1623,3.1623,2,1)



Regards,
Radovan

Edited by user 01 October 2011 19:55:15(UTC)  | Reason: Not specified

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Offline omorr  
#7 Posted : 10 January 2012 02:08:53(UTC)
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Hello,

Unfortunately, It seems that the same bug is still present in the recent v0.90

Regards,
Radovan
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Offline Andrey Ivashov  
#8 Posted : 25 January 2012 01:01:36(UTC)
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Fixed.



Best regards, Andrey Ivashov.
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thanks 1 user thanked Andrey Ivashov for this useful post.
on 25/01/2012(UTC)
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