Question 107979
 


The sum of interior angle ( Sum-of-interior-angles-n-gon) of n-gon is:

{{{Sum-of-interior-angles-n-gon = (n-2)180}}}

If we have a {{{13-gon}}}, {{{n=13}}}

Then
{{{Sum-of-interior-angles-n-gon = (13-2)180}}}
{{{Sum-of-interior-angles-n-gon = (11)180}}}
{{{Sum-of-interior-angles-n-gon = (11)180}}}

{{{Sum-of-interior-angles-n-gon = 1980}}}


If we have {{{20-gon}}}, {{{n=20}}}

{{{Sum-of-interior-angles-n-gon = (20-2)180}}}
{{{Sum-of-interior-angles-n-gon = (18)180}}}
{{{Sum-of-interior-angles-n-gon = 3240}}}


If we have {{{18-gon}}}, {{{n=18}}}

{{{Sum-of-interior-angles-n-gon = (18-2)180}}}
{{{Sum-of-interior-angles-n-gon = (16)180}}}
{{{Sum-of-interior-angles-n-gon = 2880}}}