>>from math import *
>>sin(0)
0.0
>>sin(pi)
1.2246063538223 773e016
>>sin(2*pi)
2.4492127076447 545e016
>>cos(0)
1.0
>>cos(pi)
1.0
>>cos(2*pi)
1.0
The cosine function works fine, but I'm getting weird answers for sine.
Is this a bug? Am I doing something wrong? 15 3113
Chris wrote:
>from math import * sin(0)
0.0
>sin(pi)
1.2246063538223 773e016
>sin(2*pi)
2.4492127076447 545e016
>cos(0)
1.0
>cos(pi)
1.0
>cos(2*pi)
1.0
The cosine function works fine, but I'm getting weird answers for sine.
Is this a bug? Am I doing something wrong?
What answer do you suppose you get in version 2.4?
"Chris" <ch*********@gm ail.comwrote:
>>>from math import * sin(0)
0.0
>>>sin(pi)
1.2246063538223 773e016
>>>sin(2*pi)
2.4492127076447 545e016
>>>cos(0)
1.0
>>>cos(pi)
1.0
>>>cos(2*pi)
1.0
The cosine function works fine, but I'm getting weird answers for
sine. Is this a bug? Am I doing something wrong?
>From help(math) in an interactive window:
DESCRIPTION
This module is always available. It provides access to the
mathematical functions defined by the C standard.
So what you are seeing is the behavior of the C library being exposed.
Try sin(pi*0.5) to see similar behavior to cos(pi) or cos(pi*2).
sin(pi*0.5) is what I expected, but I expected to get 0 for sin(pi).
Max Erickson wrote:
"Chris" <ch*********@gm ail.comwrote:
>>from math import * sin(0)
0.0
>>sin(pi)
1.2246063538223 773e016
>>sin(2*pi)
2.4492127076447 545e016
>>cos(0)
1.0
>>cos(pi)
1.0
>>cos(2*pi)
1.0
The cosine function works fine, but I'm getting weird answers for
sine. Is this a bug? Am I doing something wrong?
From help(math) in an interactive window:
DESCRIPTION
This module is always available. It provides access to the
mathematical functions defined by the C standard.
So what you are seeing is the behavior of the C library being exposed.
Try sin(pi*0.5) to see similar behavior to cos(pi) or cos(pi*2).
Max Erickson <ma*********@gm ail.comwrote:
>
Try sin(pi*0.5) to see similar behavior to cos(pi) or cos(pi*2).
Uhh, switch that, cos(pi*0.5)...
On 14 Oct 2006 20:33:13 0700, Chris wrote
>from math import * sin(0)
0.0
>sin(pi)
1.2246063538223 773e016
>sin(2*pi)
2.4492127076447 545e016
>cos(0)
1.0
>cos(pi)
1.0
>cos(2*pi)
1.0
The cosine function works fine, but I'm getting weird answers for sine.
Is this a bug? Am I doing something wrong?
You're apparently not correctly reading python's answer to sin(pi).
1.2246063538223 773e016 is the scientific notation for the number
0.0000000000000 001224606353822 3773, which is pretty darn close to zero, the
result you probably expected.
You're not getting *exactly* zero because you're not passing in *exactly* pi
but a close approximation of pi.
I'll leave it as an exercise for the reader to explain why cosine seems to
work fine. Hint: Look at cos(pi/2) and sin(pi/2).
Carsten
I don't understand what that number came from. My calculator gives me
cos(pi*.5) = 0, and my interpreter gives me cos(pi*0.5) =
6.1230317691118 863e017.
Max Erickson wrote:
Max Erickson <ma*********@gm ail.comwrote:
Try sin(pi*0.5) to see similar behavior to cos(pi) or cos(pi*2).
Uhh, switch that, cos(pi*0.5)...
Oh, ok that explains it. Is that why my 16bit calculator gives me 0?
Carsten Haese wrote:
On 14 Oct 2006 20:33:13 0700, Chris wrote
>>from math import *
>>sin(0)
0.0
>>sin(pi)
1.2246063538223 773e016
>>sin(2*pi)
2.4492127076447 545e016
>>cos(0)
1.0
>>cos(pi)
1.0
>>cos(2*pi)
1.0
The cosine function works fine, but I'm getting weird answers for sine.
Is this a bug? Am I doing something wrong?
You're apparently not correctly reading python's answer to sin(pi).
1.2246063538223 773e016 is the scientific notation for the number
0.0000000000000 001224606353822 3773, which is pretty darn close to zero, the
result you probably expected.
You're not getting *exactly* zero because you're not passing in *exactly* pi
but a close approximation of pi.
I'll leave it as an exercise for the reader to explain why cosine seems to
work fine. Hint: Look at cos(pi/2) and sin(pi/2).
Carsten
"Chris" <ch*********@gm ail.comwrites:
Oh, ok that explains it. Is that why my 16bit calculator gives me
0?
Your calculator is probably doing rounding without you asking for it.
Python refuses to guess what you want, and gives you the information
available.

\ "Earth gets its price for what Earth gives us."  James 
`\ Russell Lowell 
_o__) 
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