Departamento de Dibujo IES Rodrigo Caro Sección Bilingüe

Quadrilaterals

Quadrilaterals are flat shapes that have four straight sides, two of which intersect the other two. They have four sides and four angles and the sum of the angles is 360°. We label the angles with the Greek letters α, β, π and ω; the vertices are labelled with the capital letters A, B, C and D; and the sides are AB, BC, CD and DA. The diagonal of a quadrilateral is a straight line between two, non-consecutive vertices. Some quadrilaterals are parallelograms. This means that the opposite sides are parallel to each other.

Quadrilateral parallelograms

• The square. Its sides are all equal and opposite sides are parallel. All the angles are right-angles. All the diagonals are of equal length, perpendicular and intersect in the centre of the square. • Rectangle. Its parallel sides are of equal length. All its angles are right-angles. Although its diagonals are all equal and cross in the centre of the rectangle, they are not perpendicular. • Rhombus. Its opposite sides are parallel and of equal length. Its angles are not right-angles and the opposite angles are the same. Its diagonals are of different length, but they are perpendicular and they intersect in the centre of the rhomboid. • Rhomboid. Its opposite sides are parallel and of equal length. Its angles are not right-angles and the opposite angles are the same. Although its diagonals are different in length and intersect in the centre of the rhomboid, they are not perpendicular.

Square Rectangle Rhombus Rhomboid

Quadrilateral that are not parallelograms

• Isosceles trapezium. It has only two parallel sides. Its pairs of angles are equal, but they are not right-angles. Its diagonals are of equal length but are not perpendicular. • Trapezoid. None of its sides are equal nor parallel. All its angles and diagonals are different. The angles are not right-angles and the diagonals are not parallel.

Isosceles trapezium Trapezoid