ENGINEERING DRAWING ORTHOGRAPHIC PROJECTIONS

Quadrilaterals

A quadrilateral is a 2-dimensional closed shape with four straight sides.  E.g. The shape ABCD shown here is a quadrilateral. A line segment drawn from one vertex of a quadrilateral to the opposite vertex is called a diagonal of the quadrilateral.  AC is a diagonal of quadrilateral ABCD, as is BD. Types of Quadrilaterals There are seven types of quadrilaterals that can be divided into two groups:  parallelograms and other quadrilaterals. Parallelograms Quadrilaterals are called parallelograms if both pairs of opposite sides are equal and parallel to each other.  Different parallelograms and their properties are described below. Parallelogram Opposite sides of a parallelogram are parallel and equal in length. Opposite angles are equal in size. Note: Rectangle Opposite sides of a rectangle are parallel and equal in length. All angles are equal to 90°. Square Opposite sides of a square are parallel and all sides are equal in length. All angles are equal to 90°. Rhombus All sides of a rhombus are equal in length Opposite sides are parallel. Opposite angles of a rhombus are equal. The diagonals of a rhombus bisect each other at right angles. Note: Rectangles, squares and rhombuses (or diamonds) are parallelograms. Other Quadrilaterals Other quadrilaterals include trapeziums, kites and irregular quadrilaterals.