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My students were building a multifocal ellipse and... almost went crazy. My ellipse is correct, but the student's is incorrect. Although the formulas are the same. Can you guess where the error is and whether it is necessary to modify SMath so that such an error is visible? Do you know more some examples?   Ellipse4.sm (12kb) downloaded 10 time(s).Edited by moderator 08 September 2023 12:53:02(UTC)
| Reason: marked as SOLVED (not a bug)
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In fact only apparently the written formula is the same but in the first case "S" is outside the summation while in the second case it is inside the summation. You can verify this by copying and pasting the two formulas into a text editor.
sergio
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Originally Posted by: PompelmoTell  In fact only apparently the written formula is the same but in the first case "S" is outside the summation while in the second case it is inside the summation. You can verify this by copying and pasting the two formulas into a text editor.
sergio You can also select/double-click the sum symbol to check what belongs to it. ![2023-09-07 16_58_16-SMath Solver - [Ellipse4.sm].png](/forum/resource.ashx?a=47969&b=2) ![2023-09-07 16_58_04-SMath Solver - [Ellipse4.sm].png](/forum/resource.ashx?a=47970&b=2) |
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on 07/09/2023(UTC), on 07/09/2023(UTC)
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The problem is that in the first Ellipse(x,y) definition, variable S is outside Sum function, but in the definition of your students is inside: Your definition: Ellipse(x,y):sum(sqrt((x-el(X.F,i))^2+(y-el(Y.F,i))^2),i,1,N)-S Student´s definition: Ellipse(x,y):sum(sqrt((x-el(X.F,i))^2+(y-el(Y.F,i))^2)-S,i,1,N) Maybe, this explicit form is most clear for students:  Edited by user 07 September 2023 18:06:56(UTC)
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Better so 
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Rank: Advanced Member Groups: Registered, Advanced Member Joined: 06/04/2023(UTC) Posts: 339 Was thanked: 26 time(s) in 25 post(s)
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It if Mathcad 15 1 ln(x) 2 ln*x - why not 
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