[Python-ideas] Trigonometry in degrees

[Hugh Fisher]

> Date: Thu, 7 Jun 2018 12:33:29 +0000
> From: Robert Vanden Eynde <robertvandeneynde at hotmail.com>
> To: python-ideas <python-ideas at python.org>
> Subject: [Python-ideas] Trigonometry in degrees
> Message-ID:
>         >
> I suggest adding degrees version of the trigonometric functions in the math module.
>
> - Useful in Teaching and replacing calculators by python, importing something is seen by the young students much more easy than to define a function.

I agree that degrees are useful for teaching. They are also very
useful for graphics
programming, especially with my favourite OpenGL API. But I think that
the use of
radians in programming language APIs is more prevalent, so the initial advantage
of easy learning will be outweighed by the long term inconvenience of
adjusting to
what everyone else is doing.

Writing degrees(x) and radians(x) is a little inconvenient, but it
does make it clear
what units are being used. And even if your proposal is adopted, there
is still going
to be a lot of code around that uses the older math routines. With the
current API
it is a least safe to assume that angles are radians unless stated otherwise.

> - Special values could be treated, aka when the angle is a multiple of 90, young students are often surprise to see that cos(pi/2) != 0
>
> Testing for a special value Isn't very costly (x % 90 == 0) but it could be pointed out that there is a small overhead using the "degrees" equivalent of trig function because of the radians to degrees conversion And the special values testing.

Not just young students :-) I agree with this, but I would prefer the
check to be in
the implementation of the existing functions as well. Any sin/cos very
close to 0
becomes 0, any close to 1 becomes 1.

> - Standard names will be chosen so that everyone will use the same name convention. I suggest adding a "d" like sind, cosd, tand, acosd, asind, atand, atan2d.

Not "d". In the OpenGL 3D API, and many 3D languages/APIs since, appending "d"
means "double precision". It's even sort of implied by the C math
library which has
sinf and friends for single precision.

>
> Creating a new package like 'from math.degrees import cos' however I would not recommend that because "cos" in the source code would mean to lookup the import to know if it's in degrees or radians (and that leads to very filthy bugs). Also "degrees" is already so the name would have to change the name of the package.

Agree, not a good idea.

-- 

        cheers,
        Hugh Fisher