When a pair of parallel lines meet an intersecting transversal, pairs of angles with particular properties are made. Corresponding angles are equal. The lines make an F shape. Notice that the F ...

The techniques used are useful for solving all kinds of other geometry problems ... First, when a diagonal line is drawn crossing two parallel lines, it forms alternate angles that are equal.

Crows in a lab were able to distinguish shapes that exhibited right angles, parallel lines, and symmetry ... Other critters ...