Brooke S.

asked • 11/13/17

why do you have to subtract 2 in the formula (n-2)180 (this is the sum of interior angles of polygons formula).

 I am trying to explain the formula (n-2)180 used to find the sum of interior angles of polygons, I understand the formula but I'm just wondering why it's minus 2? I know that you can also split the polygon into 3 triangles and add up the sums to get 540 but why 3 triangles? Why not 5 triangles?

Mark M.

Have you drawn various polygons and divided them into triangles?
You should see that the number of triangles is always 2 less than the number of sides in the polygon.


1 Expert Answer


Matthew S. answered • 11/13/17

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