# RE: [PHP] gd project question

```Did I mention I hate math [grin]...
ok...so here we go so far...

I am passing a variable diameter of the arc (\$d),
the total number of widgets possible (\$n),
and the number of current widgets (\$x)```
```
so let's say \$d = 100
\$n = 100
\$x = 50

\$perc = \$x / \$n (0.50 or 50 %)

degree conversion = # * (180/M_PI)

asin(\$perc) converted to degrees = 30
acos(\$perc) converted to degrees = 60

my arc runs from 180 deg. to 360/0 degree, or left to right, pointing
upwards (upside down U).
i guess I am not getting my head around the numbers...is there anywhere on
the net that has a good thorough description about a process like this?

Thx.
mike

> -----Original Message-----
> From: Darren Gamble [mailto:[EMAIL PROTECTED]]
> Sent: Friday, May 31, 2002 11:40 AM
> To: 'Michael Geier'; Php-General
> Subject: RE: [PHP] gd project question
>
>
> Good day,
>
> Wow, a high school math question.
>
> You should use asin() and acos() of the angle to get the y and x
> differentials, respectively.  Multiply the result by the size of
> the needle.
>
> This assumes that your guage is oriented horizontally, and the
> needle sweeps
> from right to left, pointing upwards.  Adjust the sign or switch the
> functions around if your gauge is different.
>
> Note that the functions operate in radians (2*pi radians == 360 degrees).
>
> ============================
> Darren Gamble
> Planner, Regional Services
> Shaw Cablesystems GP
> 630 - 3rd Avenue SW
> T2P 4L4
> (403) 781-4948
>
>
> > -----Original Message-----
> > From: Michael Geier [mailto:[EMAIL PROTECTED]]
> > Sent: Friday, May 31, 2002 9:18 AM
> > To: Php-General
> > Subject: [PHP] gd project question
> >
> >
> > I have the following issue:
> >
> >     I am making a "gas guage" based on a percentage.
> >     ie.
> >             - a 180 degree arc is created
> >             - the range will be 0 to n (undetermined ammount)
> >             - there will be x number of entries
> >             - the needle will pount to a a percentage
> >               for (int)floor((x / n) * 100)
> >
> >     The issue is, I have the starting pt for the needle
> > (imagefilledarc
> >     needs the center of the 'circle' as the starting pt,
> > which is where
> >     the needle will start too), but how would I get the x|y
> > coordinates
> >     for the end of the needle based on a perentage of a half-circle
> >     (180 degree arc)?
> >
> > Appreciate any clues or ideas.
> >
> > ---
> > Michael Geier
> >
> >
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> > PHP General Mailing List (http://www.php.net/)
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> >
>
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