#!/usr/bin/env perl
use strict;
use warnings;
use Math::Trig;
use Math::BigFloat;
use feature 'say';


my $pi =  Math::BigFloat->bpi(10);

my ($run,$theta) = (3,8);

my $radians = Math::BigFloat->new($theta * $pi / 180);

#my $rise = Math::BigFloat->new($run * tan($radians)); 
my $rise = Math::BigFloat->new($run * (sin($radians) / cos($radians)))
+;

say "rise is $rise";

#rise is 0.42162250410717434055
[download]

Here is what I came up with for an equivalent. Supposedly the Math:: packages offer up to arbitrary precision or accuracy. The tan function is not working for me though, I get an error: Can't call Math::BigFloat->_cartesian, not a valid method at /usr/local/share/perl/5.14.2/Math/Complex.pm line 928. This inspired me to use a trig identity in real, well, almost real life for the first time..

So, if you can install packages, (Math::Trig and Math::BigFloat come with Perl) you can use those modules for really high accuracy calculations. If you don't then you might have to lose some accuracy

#!/usr/bin/env perl
use strict;
use warnings;
my $pi = 355/113;
my ($run,$theta) = (3,8);

my $radians = $theta*$pi/180;
my $rise = $run * (sin($radians) / cos($radians));

say "rise is $rise";
#rise is 0.421622540378273
[download]

If high accuracy is important, maybe it would better to use a better approximation of pi (although I readily admit that 355/113 is already a pretty good approximation). For example:

my $pi = 4 * atan2(1, 1);
[download]

Or perhaps making it a constant:

use constant PI => 4 * atan2(1, 1);
[download]

Both Math::Trig and Math::BigFloat provide a pi constant

$ perl -MMath::Trig -MMath::BigFloat=bpi -le " print for pi(), bpi(15)
+ "
3.14159265358979
3.14159265358979
[download]

One is never gonna outstrip a a c_double with measurements he makes with a carpenter's protractor, so Math::Trig has all the functionality I need here.

So it is that I will have a math module for perl that will give me pi and degrees_to_radians at the end of this thread.

Take a look at Math::Trig. A well tested module that does all of that and much more.

$ perl slope3.pl
Prototype mismatch: sub math1::pi () vs none at ../math1.pm line 13.
Constant subroutine pi redefined at ../math1.pm line 7.
Subroutine main::pi redefined at /usr/share/perl/5.18/Exporter.pm line
+ 66.
 at slope3.pl line 6.
Prototype mismatch: sub main::pi: none vs () at /usr/share/perl/5.18/E
+xporter.pm line 66.
 at slope3.pl line 6.
slopes are 0 5 8 11 14 30 90
runs are 2.25 3.25 4 5
An angle of 0 degrees, or 0 radians, and run of 2.25 has a rise of 0
An angle of 0 degrees, or 0 radians, and run of 3.25 has a rise of 0
An angle of 0 degrees, or 0 radians, and run of 4 has a rise of 0
An angle of 0 degrees, or 0 radians, and run of 5 has a rise of 0
An angle of 5 degrees, or 0.0872664625997165 radians, and run of 2.25 
+has a rise of 0.196849492933329
An angle of 5 degrees, or 0.0872664625997165 radians, and run of 3.25 
+has a rise of 0.284338156459253
An angle of 5 degrees, or 0.0872664625997165 radians, and run of 4 has
+ a rise of 0.349954654103696
An angle of 5 degrees, or 0.0872664625997165 radians, and run of 5 has
+ a rise of 0.43744331762962
An angle of 8 degrees, or 0.139626340159546 radians, and run of 2.25 h
+as a rise of 0.316216878080381
An angle of 8 degrees, or 0.139626340159546 radians, and run of 3.25 h
+as a rise of 0.456757712782772
An angle of 8 degrees, or 0.139626340159546 radians, and run of 4 has 
+a rise of 0.562163338809566
An angle of 8 degrees, or 0.139626340159546 radians, and run of 5 has 
+a rise of 0.702704173511957
An angle of 11 degrees, or 0.191986217719376 radians, and run of 2.25 
+has a rise of 0.437355695559867
An angle of 11 degrees, or 0.191986217719376 radians, and run of 3.25 
+has a rise of 0.631736004697585
An angle of 11 degrees, or 0.191986217719376 radians, and run of 4 has
+ a rise of 0.777521236550874
An angle of 11 degrees, or 0.191986217719376 radians, and run of 5 has
+ a rise of 0.971901545688592
An angle of 14 degrees, or 0.244346095279206 radians, and run of 2.25 
+has a rise of 0.560988006397157
An angle of 14 degrees, or 0.244346095279206 radians, and run of 3.25 
+has a rise of 0.810316009240337
An angle of 14 degrees, or 0.244346095279206 radians, and run of 4 has
+ a rise of 0.997312011372723
An angle of 14 degrees, or 0.244346095279206 radians, and run of 5 has
+ a rise of 1.2466400142159
An angle of 30 degrees, or 0.523598775598299 radians, and run of 2.25 
+has a rise of 1.29903810567666
An angle of 30 degrees, or 0.523598775598299 radians, and run of 3.25 
+has a rise of 1.87638837486628
An angle of 30 degrees, or 0.523598775598299 radians, and run of 4 has
+ a rise of 2.3094010767585
An angle of 30 degrees, or 0.523598775598299 radians, and run of 5 has
+ a rise of 2.88675134594813
An angle of 90 degrees, or 1.5707963267949 radians, and run of 2.25 ha
+s a rise of 3.67452885446896e+16
An angle of 90 degrees, or 1.5707963267949 radians, and run of 3.25 ha
+s a rise of 5.3076527897885e+16
An angle of 90 degrees, or 1.5707963267949 radians, and run of 4 has a
+ rise of 6.53249574127815e+16
An angle of 90 degrees, or 1.5707963267949 radians, and run of 5 has a
+ rise of 8.16561967659768e+16
pi is 3.14159265358979
$ cat slope3.pl
#!/usr/bin/perl -w
use strict;
use 5.010;
BEGIN { push @INC, ".."; }
use math1;
use Math::Trig;

my @slope = (0.0, 5.0, 8.0, 11.0, 14.0, 30.0, 90.0);
say "slopes are @slope";

my @run = (2.25, 3.25, 4, 5);
say "runs are @run";



foreach my $var1 (@slope) {
   my $s = degrees_to_radians($var1);
   foreach my $var2 (@run) {
   my $t = $var2 * tan($s);
     
  say "An angle of $var1 degrees, or $s radians, and run of $var2 has 
+a rise of $t";
 } 
 } 

my $a = pi();
say "pi is $a";
__END__ 
$
[download]

I made this as quick and dirty as I had to to get results. I like the results partially, in that I believe they're correct. The aspiration to have my own module was admirable for its valor, but not with its merits. I figured out that what I was doing came within spitting distance of *literally* re-inventing the circle.

$ cat math1.pm
package math1;
require Exporter;

our @ISA = qw(Exporter);
our @EXPORT = qw( pi degrees_to_radians);

sub pi{
use 5.010;
use Math::Trig ':pi';

my $a = pi;
return $a;
}

sub degrees_to_radians{
use 5.010;
use Math::Trig qw(deg2rad);

my $a = shift;
my $b = deg2rad($a);
return $b;
}

1;

$
[download]

I'm still fishing for people's experience with this, but I'll post a cleaned-up version of this that relies on cpan properly, instead of wrapping the calls and confusing perl.exe. Thanks all for comments.

Although it probably does not have any consequences here, I would suggest that you avoid using the $a (and $b) variable, because $a and $b are special purpose global variables used for sorting data (and a few other specific uses).