Perpendicular lines Two lines are perpendicular if they cross at right angles. You can test this by extending the lines until they cross (if they do not cross then they are parallel). Where the [...]
The perimeter of this rectangle is in dark green. The perimeter of a square or a triangle is the distance all the way around the edge - the green strip in this picture. The circumference of [...]
Two parallel lines Two lines are parallel if they are in the same plane but they can go on forever without ever crossing. You can test this by seeing if you can [...]
