The dashes on the lines show they are equal in length ... you can use this fact to find missing angles in a quadrilateral. Take a look at this shape. Let's work out the missing angle labelled ...

Polygons have names that show the number of sides they have ... Look at how these shapes have been sorted. Remember a quadrilateral is any shape with 4 straight sides. Now the shapes have been ...

Crows can recognize geometric patterns, suggesting that humans aren't unique in understanding shape structure.