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| Date | Fri, 15 Feb 2013 11:47:33 -0800 |
| From | Gary Herron <gherron@digipen.edu> |
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| Subject | Re: python math problem |
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On 02/15/2013 11:39 AM, Kene Meniru wrote: > I am trying to calculate the coordinates at the end of a line. The length > and angle of the line are given and I am using the following formula: > > x = (math.sin(math.radians(angle)) * length) > y = (math.cos(math.radians(angle)) * length) > > The following are sample answers in the format (x, y) to the given > length/angle values of the line: > > 120/0 = (0.0, 25.0) > 120/89 = (24.9961923789, 0.436310160932) > 120/90 = (25.0, 1.53075794228e-15) > 120/91 = (24.9961923789, -0.436310160932) > > Why am I getting a string number instead of the expected answer for 120/90 > which should be (25.0, 0.0). This happens at all multiples of 90 (i.e. 180 > and 270) > Floating point calculations on a computer (ANY computer, and ANY programming language) can *never* be expected to be exact! (Think about 1/3 , PI, and sqrt(2) for instance.) The values written out as 1.53075794228e-15 is the (scientific notation) representation of .00000000000000153075794228. Is that not close enough to zero for your purposes? (Or is it that you don't understand the 'e-15' portion of the output?) -- Dr. Gary Herron Department of Computer Science DigiPen Institute of Technology (425) 895-4418
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Re: python math problem Gary Herron <gherron@digipen.edu> - 2013-02-15 11:47 -0800
Re: python math problem Nobody <nobody@nowhere.com> - 2013-02-16 13:55 +0000
Re: python math problem Chris Angelico <rosuav@gmail.com> - 2013-02-17 01:30 +1100
Re: python math problem Roy Smith <roy@panix.com> - 2013-02-16 09:32 -0500
Re: python math problem Dave Angel <davea@davea.name> - 2013-02-16 13:24 -0500
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