Quadrilaterals

A quadrilateral is a plane figure with four sides and four angles. We can classify quadrilaterals by the characteristics of their sides and angles

In a parallelogram, opposite sides are parallel and congruent and opposite angles are congruent. A rhombus is a parallelogram with four congruent sides

A rectangle is a parallelogram with four right angles. A square is a rectangle with four congruent sides

A trapezoid is a quadrilateral with exactly two parallel sides

A diagonal of a polygon is a line segment that connects two of the vertices of the polygon

The diagonal divides the quadrilateral into two triangles

The sum of the measures of the angles of any triangle is always 180 degrees, no matter the size

Since two triangles are formed when we draw a diagonal in a quadrilateral, the sum of the measures of the angles is 180⁰ + 180⁰ = 360⁰

A quadrilateral is a polygon that has 4 sides

Quadrilaterals are divided into two major groups - "parallelograms" and "not parallelograms"

The quadrilaterals that have two pairs of parallel sides are called parallelograms

The special types of parallelograms include rectangles, rhombuses, and squares:
A rhombus has 4 sides that are all the same length
A rectangle has 4 right angles. The sides do not all have to be the same length
A square has 4 right angles. Its 4 sides are all the same length