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#11
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How do I Calculate PI in an Excel formula?
On Sun, 11 Jan 2009 11:34:01 -0800, jollydottie
wrote: on Excell =E15+14.86*D15*PI()*F15*0.85 =139.0444 on my calc =20 + 14.86 = 34.86 x 6 = 209.16 x PI = 14.462 x .500 = 7.23 x .85 = 6.1465- this is the right answer So what am I doing wrong? 1. If by PI you mean the ratio of the circumference to the diameter of a circle, then your calculated result is incorrect as the value of PI is a bit more than 3 and no way can 209.16 x PI be less than 627. Your calculator seems to be giving you a result of 14.462, if I understand what you have written above. 2. In addition to that, you are probably not understanding the order in which Excel performs operations in formulas, which is documented in HELP. You can use parentheses to control the calculation order, so your Excel formula might read: =(E15+14.86)*D15*PI()*F15*0.85 But you still have your calculator doing: 209.16 * PI -- 14.462 which, since PI = 3.14159..., is incorrect. --ron |
#12
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How do I Calculate PI in an Excel formula?
ATAN(1), not ATAN(4), I think?
But yes, it'll work to 15 sig figs, not just 10. -- David Biddulph Bernard Liengme wrote: Why only 10 decimal places? Mathematically Atan(4) = pi()/4, Then 4*ATAN(4) and PI() must give exactly the same answer within the precision of Excel (15 decimals) best wishes "Rick Rothstein" wrote in message ... If you have trouble remembering or finding the constant value, but have a good memory for simple formulas, this will generate PI to 10 significant figures (usually more than enough for any calculation involving it)... =4*ATAN(1) -- Rick (MVP - Excel) "jollydottie" wrote in message ... Using the calculator I get a different answer, if PI = 3.162. then *3.162 in Excell should give me the right answer but it doesn't. |
#13
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How do I Calculate PI in an Excel formula?
Hi,
we've exhausted this topic area so I thought I would throw in - PI has been calculated to 2 billion digits, probably more by now, but Excel is not prepared for more than 15. Also, although this is not the core problem, computers work in binary, we work in decimals - which leads to approximations. Here is everything you need to know about this issue (and more): http://support.microsoft.com/kb/78113/en-us http://support.microsoft.com/kb/42980 http://support.microsoft.com/kb/214118 http://www.cpearson.com/excel/rounding.htm http://docs.sun.com/source/806-3568/ncg_goldberg.html -- If this helps, please click the Yes button Cheers, Shane Devenshire "jollydottie" wrote: Using the calculator I get a different answer, if PI = 3.162. then *3.162 in Excell should give me the right answer but it doesn't. |
#14
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How do I Calculate PI in an Excel formula?
Thank you all, I have found my error.
"Ron Rosenfeld" wrote: On Sun, 11 Jan 2009 11:34:01 -0800, jollydottie wrote: on Excell =E15+14.86*D15*PI()*F15*0.85 =139.0444 on my calc =20 + 14.86 = 34.86 x 6 = 209.16 x PI = 14.462 x .500 = 7.23 x .85 = 6.1465- this is the right answer So what am I doing wrong? 1. If by PI you mean the ratio of the circumference to the diameter of a circle, then your calculated result is incorrect as the value of PI is a bit more than 3 and no way can 209.16 x PI be less than 627. Your calculator seems to be giving you a result of 14.462, if I understand what you have written above. 2. In addition to that, you are probably not understanding the order in which Excel performs operations in formulas, which is documented in HELP. You can use parentheses to control the calculation order, so your Excel formula might read: =(E15+14.86)*D15*PI()*F15*0.85 But you still have your calculator doing: 209.16 * PI -- 14.462 which, since PI = 3.14159..., is incorrect. --ron |
#15
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How do I Calculate PI in an Excel formula?
While Excel will only display 15 digits, its value for pi is correct to
almost 17 digits. To 17 digits, Excel's value for pi is 3.1415926535897931 compared to the actual 17 digit approximation to pi of 3.1415926535897932 Jerry "Shane Devenshire" wrote: .... PI has been calculated to 2 billion digits, probably more by now, but Excel is not prepared for more than 15. .... |
#16
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How do I Calculate PI in an Excel formula?
No, I think ATAN(1) = pi()/4 so 4*ATAN(1) = pi
Please check on worksheet and let me know if I am wrong - it has happened before! Happy New Year -- Bernard remove caps from email "David Biddulph" groups [at] biddulph.org.uk wrote in message ... ATAN(1), not ATAN(4), I think? But yes, it'll work to 15 sig figs, not just 10. -- David Biddulph Bernard Liengme wrote: Why only 10 decimal places? Mathematically Atan(4) = pi()/4, Then 4*ATAN(4) and PI() must give exactly the same answer within the precision of Excel (15 decimals) best wishes "Rick Rothstein" wrote in message ... If you have trouble remembering or finding the constant value, but have a good memory for simple formulas, this will generate PI to 10 significant figures (usually more than enough for any calculation involving it)... =4*ATAN(1) -- Rick (MVP - Excel) "jollydottie" wrote in message ... Using the calculator I get a different answer, if PI = 3.162. then *3.162 in Excell should give me the right answer but it doesn't. |
#17
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How do I Calculate PI in an Excel formula?
You are correct that ATAN(1) = pi()/4 and that 4*ATAN(1) = pi
But in your previous message you had said Atan(4) = pi()/4 and 4*ATAN(4) It has obviously been a long year, Bernard. :-) -- David Biddulph Bernard Liengme wrote: No, I think ATAN(1) = pi()/4 so 4*ATAN(1) = pi Please check on worksheet and let me know if I am wrong - it has happened before! Happy New Year "David Biddulph" groups [at] biddulph.org.uk wrote in message ... ATAN(1), not ATAN(4), I think? But yes, it'll work to 15 sig figs, not just 10. -- David Biddulph Bernard Liengme wrote: Why only 10 decimal places? Mathematically Atan(4) = pi()/4, Then 4*ATAN(4) and PI() must give exactly the same answer within the precision of Excel (15 decimals) best wishes "Rick Rothstein" wrote in message ... If you have trouble remembering or finding the constant value, but have a good memory for simple formulas, this will generate PI to 10 significant figures (usually more than enough for any calculation involving it)... =4*ATAN(1) -- Rick (MVP - Excel) "jollydottie" wrote in message ... Using the calculator I get a different answer, if PI = 3.162. then *3.162 in Excell should give me the right answer but it doesn't. |
#18
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How do I Calculate PI in an Excel formula?
On Jan 11, 1:22*pm, Shane Devenshire
wrote: PI has been calculated to 2 billion digits, probably more by now, but Excel is not prepared for more than 15. * Also, although this is not the core problem, computers work in binary, we work in decimals - which leads to approximations. In Excel 2003, the binary representation of PI() is exactly 3.14159265358979,311599796346854418516159057617187 5. According to online sources, the value of pi calculated to that many decimal places (plus 2) is 3.14159265358979,323846264338327950288419716939937 510. (The comma marks 15 significant digits to the left.) I'm too lazy to compute the percent error :-). |
#19
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How do I Calculate PI in an Excel formula?
On Jan 11, 12:02*pm, "Bernard Liengme"
wrote: Then 4*ATAN(4) and PI() must give exactly the same answer within the precision of Excel (15 decimals) Yes. Both 4*ATAN(1) and PI() are represented in binary exactly as 3.14159265358979,311599796346854418516159057617187 5. (The comma marks 15 significant digits to the left.) At least, that is the case for Excel 2003. |
#20
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How do I Calculate PI in an Excel formula?
Want to inform us, seeing as we took the time to try and help?
-- __________________________________ HTH Bob "jollydottie" wrote in message ... Thank you all, I have found my error. "Ron Rosenfeld" wrote: On Sun, 11 Jan 2009 11:34:01 -0800, jollydottie wrote: on Excell =E15+14.86*D15*PI()*F15*0.85 =139.0444 on my calc =20 + 14.86 = 34.86 x 6 = 209.16 x PI = 14.462 x .500 = 7.23 x .85 = 6.1465- this is the right answer So what am I doing wrong? 1. If by PI you mean the ratio of the circumference to the diameter of a circle, then your calculated result is incorrect as the value of PI is a bit more than 3 and no way can 209.16 x PI be less than 627. Your calculator seems to be giving you a result of 14.462, if I understand what you have written above. 2. In addition to that, you are probably not understanding the order in which Excel performs operations in formulas, which is documented in HELP. You can use parentheses to control the calculation order, so your Excel formula might read: =(E15+14.86)*D15*PI()*F15*0.85 But you still have your calculator doing: 209.16 * PI -- 14.462 which, since PI = 3.14159..., is incorrect. --ron |
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