All the diagonals of a convex polygon lie entirely inside the polygon.
In a concave polygon some diagonals will lie outside the polygon.
Each angle of a convex polygon is less than 180°.
At least one angle of a concave polygon is more than 180°.
All the sides and angles of a regular polygon are equal.
In an irregular polygon, all the sides and angles are not equal.
Sum of interior angles of a polygon with n sides = (n – 2) x 180°
Each interior angle (regular polygon) = [(n – 2) × 180°] / n.
The sum of all the exterior angles of a convex polygon of n sides is always equal to 360°.
The sum of all the angles of a quadrilateral is 360°.
Opposite sides of a parallelogram are equal.
Opposite angles of a parallelogram are equal.
Diagonals of a parallelogram bisect each other.
Adjacent angles of a parallelogram are supplementary.
All sides of a rhombus are of equal length.
The diagonals of a rhombus are perpendicular bisectors of each other.
Opposite angles of a rhombus are of equal measure.
Opposite sides of a rhombus are parallel to each other.
The opposite sides of a rectangle are parallel to each other and are equal in length.
All angles of a rectangle are right angles.
The diagonals of a rectangle are equal in length and bisect each other.
A square is a rhombus in which each interior angle is equal to 90° and both the diagonals are equal.
A square is a rectangle in which all sides are equal and diagonals intersect at right angle.
The diagonals of a square are perpendicular bisectors of each other.
Keywords: Plane surface, Plane curve, Trapezium, Kite.