degrees and radians.

[Tim Hammerquist]

Simon Foster graced us by uttering:
> "Tim Hammerquist" <tim at vegeta.ath.cx> wrote:
> > > Radians are what trig is based on. Otherwise the formula for the
> > > area of a circle would be 'A = 360r'; since when does a unit
> > > circle have an area of 360 square units?
> 
> Where do you get this from?  A = pi * r^2?

You're right. Not enough coffee and too much time passed since college
trig. =) Correction:

: If trig were based on degrees, the following would be true for a
: unit circle:
:
:   [ A = (180 * r^2) = 180 sq. units ]
:   [ C = (360 * r)   = 360 units     ]

Thus:

  "since when does a unit circle have an area of 180 sq. units?"
                                                 ^^^^^^^^^^^^^

> > > OTOH, `man 3 sin` on my system documents the sin() function of
> > > the C math library _is_ documented as taking radians. On a POSIX
> > > system, this is usually what is called by Ruby's Math.sin()
> > > method.
> 
> Maybe he's not on Unix?

My handy copy of the Turbo C++ 3.0 Library Reference manual from my
MS-DOS version of the software also documents sin() as taking a value in
radians. (C)1990.  A.D.  So this is far from new. One might say it's a
standard...  A trig calculator's default setting doesn't dictate the
default of the world at large.

Furthermore, not all *nix systems are POSIX-compliant. And very few
POSIX-compliant systems are _completely_ compliant with the POSIX
standard.

My only intent in mentioning POSIX was that on most *nix systems (esp.
POSIX ones), you can #include<math.h> and compile and expect to call
a sin() function (that, btw, takes its argument in radians). Other
PC-oriented operating systems lack a standard math lib "out-of-the-box".

Tim Hammerquist
-- 
guru, n: a computer owner who can read the manual.