[ python-Bugs-1053629 ] Why is this expression == False?
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Wed Oct 27 05:35:42 CEST 2004
Bugs item #1053629, was opened at 2004-10-25 06:09
Message generated for change (Comment added) made by tim_one
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Category: None
Group: Python 2.3
Status: Closed
Resolution: Invalid
Priority: 5
Submitted By: Alexander Rødseth (alexanro)
Assigned to: Nobody/Anonymous (nobody)
Summary: Why is this expression == False?
Initial Comment:
I am not sure if this is a bug or not, but I'm very curious
of the reason for the following result:
>>> from math import *
>>> theta = pi
>>>
e**(complex(0,1)*theta)==cos(theta)+complex(0,1)*sin(theta)
False
This is supposed to be True, unless I've made some typo
or made some other mistake. It's a version of Euler's
equation.
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>Comment By: Tim Peters (tim_one)
Date: 2004-10-26 23:35
Message:
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Try this one:
>>> 37.0 / 3 / 3 * 9 == 37.0
False
Worry about transcendentals after making peace with basic
float arithmetic <wink>.
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Comment By: Michael Hudson (mwh)
Date: 2004-10-25 07:09
Message:
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Heh. Walter, the two numbers you show are in fact equal. Also,
the expression is True for me. I wonder what platform Alexander
is on -- but not very much, attempting to verify equalities
involving transcedental quantities using finite precision arithmetic
is always going to be risky.
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Comment By: Walter Dörwald (doerwalter)
Date: 2004-10-25 06:35
Message:
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This is due to rounding errors:
>>> from math import *
*>>> e**(1j*pi)
(-1+1.2246063538223773e-16j)
*>>> cos(pi)+1j*sin(pi)
(-1+1.2246063538223773e-16j)
Closing the bug report
----------------------------------------------------------------------
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