Quadrilaterals are shapes with four sides.
In the following diagrams the arrows indicate parallel lines; the marks on lines indicate lines that are bisected; angles with the same value have the same colour; filled angles are bisected by the diagonals.
|All four interior angles are right angles|
|A rectangle where all sides are of equal length|
|Two sets of parallel sides|
|A parallelogram with equal length sides|
|A quadrilateral reflected in the line BD|
One set of parallel sides
DAB + CDA = 180º
ABC + BCD = 180º
Give one difference between a trapezium and a parallelogram.
Or the opposite angles on a parallelogram are equal, which is not true for a trapezium.
Answer: A parallelogram has two sets of parallel sides: a trapezium only has one set
What is the size of the angle CDA in this kite?
The angle BCD, directly opposite DAB, is equal to that angle and is 100º.
There are 360º in a quadrilateral: 360 - 100 - 100 - 100 = 60º