This document discusses properties of polygons, including:
1) The sum of interior angles in a triangle is 180 degrees, and the sum of interior angles in an n-sided polygon is (n-2) x 180 degrees.
2) The sum of angles can be 900 degrees for a heptagon/septagon with 7 sides, but cannot be 1600 degrees as that number of degrees does not correspond to a whole number of sides.
3) The sum of outer angles (exterior angles) of any polygon is always 360 degrees, with the outer angles at each vertex summing to 180 degrees.