Constructions

Geometric Constructions ... Animated!

Compass

"Construction" in Geometry means to draw shapes, angles or lines accurately.

These constructions use only compass, straightedge (i.e. ruler) and a pencil.

This is the "pure" form of geometric construction - no numbers involved!

straightedge
straightedge

 

Learn these two first, they are used a lot:
Line Bisector Line Bisector
Angle Bisector Angle Bisector
And it is useful to know how to do 30°, 45° and 60° angles. You can use the angle bisector method (above) to create other angles, such as 15°, etc:
30 Degree Angle 30 Degree Angle
45 Degree Angle 45 Degree Angle
60 Degree Angle 60 Degree Angle
Equilateral Triangle Equilateral Triangle
Points and Lines:
Perpendicular to a Point on a Line Perpendicular to a Point on a Line
Perpendicular to a Point NOT on a Line Perpendicular to a Point NOT on a Line
Parallel Line through a Point Parallel Line through a Point
Same (Congruent) Angle Same (Congruent) Angle
Cut a line into N segments Cut a line into N segments
Circles:
Center of a Circle Center of a Circle
Point to Tangents on a Circle Point to Tangents on a Circle
Inscribe a Circle in a Triangle Inscribe a Circle in a Triangle
Circumscribe a Circle on a Triangle Circumscribe a Circle on a Triangle
Circle touching 3 Points Circle touching 3 Points
And for the "Master Class", a Pentagon
Pentagon Pentagon

 

(Note: You can also see how to Use the Protractor, Use the Drafting Triangle and Ruler, and How to construct a Triangle With 3 Known Sides, but they are not "pure" geometric constructions.)

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