Formula

• The general formula to find the length [latex]a[/latex] of the apothem of a regular polygon with [latex]n[/latex] sides that have a length of [latex]c[/latex] is: [latex]a=\dfrac{c}{2\textrm{tan}({\frac{180}{n})}}[/latex].

• The length [latex]a[/latex] of the apothem of a regular polygon with n sides can also be expressed using the measure of the radius of the circle circumscribed around the polygon:

[latex]a=r \cos{( \frac{180}{n})}[/latex].