​Quadrilaterals are classified according to the number of sets or parallel sides.

​After we look at the number of parallel sides, we consider the number of equal sides and equal angles.

​Lines of Symmetry

A line of symmetry in a quadrilateral is a line that, when folded along, divides the quadrilateral into two identical, mirror-image halves.

​Rectangles and Squares

​If a quadrilateral has 4 right angles, it is a rectangle.

If it ALSO has 4 equal sides, it is ALSO a square.

So ALL squares are also rectangles, but only SOME rectangles are also squares.

​Quadrilaterals are classified according to the number of sets or parallel sides.

​After we look at the number of parallel sides, we consider the number of equal sides and equal angles.

​When a quadrilateral is a parallelogram, the diagonals BISECT each other. (parallelogram, rectangle, rhombus, square)

When the quadrilateral has right angles, the diagonals are EQUAL. (rectangle, square)

When the quadrilateral has 4 equal sides, the diagonals are PERPENDICULAR (rhombus, square).

​The angles of a quadrilateral all add up to 360.

If one angle is missing, add the angles you do know and subtract from 360.

​5. Interior angles add up to 360.