1.2 Basic Constructions

Construct copies of segments and angles
Construct segments, perpendicular bisectors of segments, and bisectors of angles
Apply construction to problems involving portions of segments and angles

Assignment

Three vocabulary definitions
p20 10–19, 21–25 (15 problems, PDF link)

If we’re going to spend all this time looking and figures and shapes, it’ll be helpful to know how to draw basic geometric figures, or constructions. The trick is that we’ll do it without measuring anything, instead using only a compass and a straightedge.

We’ll only cover four simple constructions and leave the more complex drawings, like polygons, as side activities later in the year.

If this ends up being something that piques your interest, Euclidea is a game centered around constructions. You can play in a browser or download it as an app.

Pictures over Words

Since this topic is less conceptual and more of a how-two, I’m not going to bother reinventing the wheel. Directions and accompanying animations for each construction are below. I’ll demo them in class, but these should work in case you miss it or need a refresher.

A couple quick definitions: a bisector is a line that divided something in half, and perpendicular means it forms a right (90°) angle.