Introduction
Rectilinear Figure : A plane figure bounded by straight lines is called a rectilinear figure.
Theorem1
In a polygon of 'n' sides, the sum of the interior angles is equal to (2n - 4) right angles.
Quadrilaterals
A quadrilateral is a polygon having 4 sides. ABCD is a quadrilateral and AC and BD are its diagonals.
Theorem2
The opposite sides and angles of a parallelogram are equal.
Theorem3
The diagonals of a parallelogram bisect each other.
Theorem4
If a pair of opposite sides of a quadrilateral is equal and parallel, it is a parallelogram.
Theorem5
A rhombus is a parallelogram whose diagonals meet at right angles.
Construction of Special types of Quadrilaterals
(a) Two sides and an angle are given. (b) Diagonals and the angle included by them are given.
Construction of Special types of Quadrilaterals (cont..)
(a) Construction of a Regular Hexagon. (b) Construction of a Regular Pentagon.
Summary
If the sides of a convex polygon are produced, in order, the sum of the exterior angles is 4 right angles.
