Negative result of ((a+b+c)*(b+c-a)*(c+a-b)*(a+b-c)) is not possible if a,b,
and c are lengths of a triangle's sides.  The first term will always be
obviously positive, and so will the other three terms -- they  are simply
the sum of  the lengths of two sides less the third side, and you can't have
a triangle where that isn't true.  It's most likely that your input numbers
to the formula are incorrect.  Trace that to find your problem.

On 12/14/06, Merrill, Jason <[EMAIL PROTECTED]> wrote:

I'm trying to figure the area of a triangle in Actionscript using the
perimeter values only, not the traditional simple formula:

     area = (height/2)*base

because figuring the height is tricky given the triangle will be drawn
in odd ways (i.e. a not horizontally alinged base), so I am exploring
other triangle area forumulas that only take in the perimiter values
(a,b,c), like Heron's formula or this one, which I like:

given a,b,c are the length of the sides of the triangle, then the
formula is:

   squareRoot of: (a+b+c)(b+c-a)(c+a-b)(a+b-c)
_______________________________________
                             4

So in trying to translate that to actionscript, I wrote:

        public static function areaOfTriangle(a:Number, b:Number,
c:Number):Number{
                return (Math.sqrt((a+b+c)*(b+c-a)*(c+a-b)*(a+b-c)))/4;
        }

But the problem is (a+b+c)*(b+c-a)*(c+a-b)*(a+b-c) results in a negative
number, and this the square root cannot be taken.  Or perhaps I am
interpreting the forumula incorrectly:
http://mathworld.wolfram.com/TriangleArea.html

What am I doing wrong here?  Thanks.

Jason Merrill
Bank of America
Learning & Organizational Effectiveness




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