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Polygon diagonal count: Side count Calculator

Polygon diagonal count: Calculate side count from Total diagonals. Check the formula, input units and worked result on this page.

Enter your values

Formula symbol: D. Enter a numeric value. Use a whole number. Use a non-negative value.

Use a decimal point, without thousands separators.

Lengths use cm, areas cm² and volumes cm³ on one consistent scale. The positive real branch is selected; the supplied quantities must describe the stated shape.
Example result
Side count
5

The initial result uses the example values. Enter your own values and calculate again.

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How it works

Sides joining adjacent vertices are not diagonals. Each diagonal is counted at both ends, so the total divides by two; the inverse must give an integer side count. This form solves for side count; enter the known quantities in Total diagonals.

Inputs and units
Polygon diagonal count: Side count Calculator · Inputs and units
InputExample valueWhat to enter
Total diagonals5Formula symbol: D. Enter a numeric value. Use a whole number. Use a non-negative value.
n = (3+√(9+8D))/2

Worked example

Show example inputs and results

This example is generated by the same calculation engine using the starting values in the form. Your own inputs produce your own result.

Total diagonals
5

Complete example results

Side count
5

Reading the result

The result solves for side count from the entered quantities. Check the result unit and the formula conditions before using it.

Questions and answers

Can I use the example values for my own calculation?

The example values illustrate the calculation. Replace every input with your own information, especially dates, rates and the selected operation.

When can I use the side count result?

Lengths use cm, areas cm² and volumes cm³ on one consistent scale. The positive real branch is selected; the supplied quantities must describe the stated shape.

Why are some results rounded?

Results display up to 8 decimal places. Calculations use the unrounded values; very small values use scientific notation. JavaScript floating-point arithmetic can introduce tiny rounding differences.

Are my inputs sent to a server?

The calculator processes inputs in your browser. Its code does not send your values to a server.

Method sources: openstax.org

Methods & accuracy

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