Polygon called figure on the plane, consisting of three or more sides that intersect at three or more points.
A polygon is convex if every angle of less than 180 ?.
Usually regarded as polygons is convex polygons.
To find the angles of a polygon need to have a minimum set of baseline data.
Suppose a polygon known length of its sides.
A polygon is called regular if its sides are equal to each other, as well as all the angles are equal.
If it is known beforehand that the polygon is correct, then the angles can be calculated by the formula
?? = 180? * (N - 2) / n, where n - the number of sides of the polygon.
For example, in the case of a regular octagon
?? = 180? * (8 - 2) / 8 = 135?
For irregular triangle with known parties, the angles can be calculated by the cosine, for example, for an angle ?? in the above figure formula becomes
cos ?? = (B + c -?? A?) / 2 • b • c
To find irregular polygons angles to the number of sides greater availability of 3 lengths of the sides is not a sufficient condition.