Chalkboard Geometry: Construct a Perpendicular Line

Chris demonstrates a classic geometric construction problem: drawing a perpendicular line from a given point C to a line segment AC using a circle arc template and a straightedge. He does this on a blackboard and a piece of chalk. He highlights the step-by-step process involved in achieving this construction.

1. Placing the Circle Arc Template: Chris centres the circle arc template at point C and uses it to draw an arc that intersects line segment AB at two points.
2. Perpendicular Bisector Construction: The construction now resembles the construction of a perpendicular bisector. By drawing arcs from the two new points, he establishes two points (including the point C) as the intersection of these arcs.
3. Drawing the Perpendicular Line: Finally, Chris uses the straight edge to draw the line segment from C to the previous new point, which is perpendicular to line segment AB as required.

So, there you have it - a beautiful, perfectly straight line that starts from a point, C, and is perpendicular to the line segment AB. This construction is a classic problem in geometry. It hows us how lines and points can come together to create something new and wonderful.