Description
Return (firstX × secondY-secondX × firstY)/2 as signedAreaContribution.
Polygon formulas combine edge, angle, and area contributions under a stated shape model. A single shoelace term or turning-angle ratio is only part of a full polygon computation and does not independently validate its boundary.
Return (firstX × secondY-secondX × firstY)/2 as signedAreaContribution.
When to use this tool
Use Polygon Signed Area Edge Term when you need a polygon dimension, angle, or local accumulation term.
How to use the tool and how it works
- Enter firstX, firstY, secondX, secondY. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read signedAreaContribution. Use the output convention below.
Return (firstX × secondY-secondX × firstY)/2 as signedAreaContribution.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| firstX | First X | Required. Finite number. |
| firstY | First Y | Required. Finite number. |
| secondX | Second X | Required. Finite number. |
| secondY | Second Y | Required. Finite number. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| signedAreaContribution | Signed Area Contribution | Required. Finite number. |
{
"input": {
"firstX": 2,
"firstY": 1,
"secondX": 3,
"secondY": 4
},
"output": {
"signedAreaContribution": 2.5
}
}Limitations and assumptions
- Coordinates use one planar Cartesian frame and output is squared length; this is one shoelace edge term, not a complete polygon area or a check of closure and self-intersection.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Evaluate the complete ordered boundary for area, winding, and validity. Use a general polygon method when regularity, simplicity, convexity, or uniform shape assumptions do not hold.
References
Similar or alternative tools
- Polygon Boundary Turn Sum
Sum supplied signedTurnsRadians and divide by 2π for winding.
- Regular Polygon Apothem Radius Ratio
Require sides 3-1000000 and return cos(π/sides).