[Python-ideas] Fwd: Trigonometry in degrees
stephanh42 at gmail.com
Wed Jun 13 03:51:04 EDT 2018
Op di 12 jun. 2018 12:41 schreef Nathaniel Smith <njs at pobox.com>:
> On Tue, Jun 12, 2018, 00:03 Stephan Houben <stephanh42 at gmail.com> wrote:
>> Hi all,
>> I wrote a possible implementation of sindg:
>> This code first reduces the angle to the [0,90] interval.
>> After doing so, it can be observed that the simple implementation
>> produces exact results for 0 and 90, and a result already rounded to
>> nearest for
> You observed this on your system, but math.sin uses the platform libm,
> which might do different things on other people's systems.
Ok, I updated the code to treat all the values 0, 30, 45, 60 and 90
>> For 30 and 45, this simple implementation is one ulp too low.
>> So I special-case those to return the correct/correctly-rounded value
>> Note that this does not affect monotonicity around those values.
> Again, monotonicity is preserved on your system, but it might not be on
> others. It's not clear that this matters, but then it's not clear that any
> of this matters...
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