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From: "Steven G. Kargl" <sgk@REMOVEtroutmask.apl.washington.edu>
Newsgroups: comp.lang.fortran
Subject: Re: Angle Units For Trig Functions
Date: Wed, 23 Oct 2024 22:22:48 -0000 (UTC)
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On Wed, 23 Oct 2024 21:21:41 +0000, Neil wrote:

> Steven G. Kargl <sgk@removetroutmask.apl.washington.edu> wrote:
>> On Wed, 23 Oct 2024 06:25:02 +0000, Lawrence D'Oliveiro wrote:
>> 
>>> On Wed, 23 Oct 2024 07:59:24 +0200, R Daneel Olivaw wrote:
>>> 
>>>> Lawrence D'Oliveiro wrote:
>>>>
>>>>> On Wed, 23 Oct 2024 04:06:26 -0000 (UTC), David Jones wrote:
>>>>> 
>>>>>> Did you take a high school trigonometry class?
>>>>> 
>>>>> You seem obsessed with that.
>>> 
>>> So your favourite functions return an exact result for sin 30°. Do
>>> they return an exact result for cos 30° as well?
>>> 
>>> 
>> Nope.  For REAL x, COSD(x) returns an exact result for all N >= 0 that
>> satisfies 60+N*360 < 2**23.
>> 
>> 
> Could you give an example of where sind and cosd might be of use in a
> piece of numerical software?

I don't use degree trig functions in my codes. Conversion of lat/long
to UTM may be a place one might use sind and/or cosd.  Seattle is
at 47.6061° N, 122.3328° W.  I've never seen someone refer to the
location as 0.83088 N, 2.13511 W.

-- 
steve