Leaving Cert Ordinary Constructions
The Leaving Cert Ordinary course contains 19 geometry constructions, 13 of which you will have already covered in Junior Cert constructions.
Some of these first 13 form the basic steps of the more advanced constructions, so it is important to master these first. When you are comfortable with constructions 1 to 13, you can move on to the remaining 6 constructions which are required for the Leaving Cert Ordinary course.
Geometry constructions have been examined almost every year in the Leaving Cert Ordinary exam. If you are aiming for a high grade, you can’t afford to neglect this part of the course.
For general guidance on how to learn and revise constructions, click here.
Here’s the full list of LCO constructions, and the demo videos are embedded below this.
Construction 1 – Bisector of an angle, using only compass and straight edge
Construction 2 – Perpendicular bisector of a segment, using only compass and straight edge
Construction 4 – Line perpendicular to a given line l, passing through a given point on l
Construction 5 – Line parallel to given line, through a given point
Construction 6 – Division of a line segment into 2, or 3 equal segments without measuring it
Construction 8 – Line segment of a given length on a given ray
Construction 9 – Angle of a given number of degrees with a given ray as one arm
Construction 10 – Triangle, given lengths of 3 sides
Construction 11 – Triangle, given SAS data
Construction 12 – Triangle, given ASA data
Construction 13 – Right-angled triangle, given length of hypotenuse and one other side
Construction 14 – Right-angled triangle, given one side and one of the acute angles
Construction 15 – Rectangle given side lengths
Construction 16 – Circumcentre and circumcircle of a given triangle, using only straight edge and compass
Construction 17 – Incentre and incircle of a triangle of a given triangle, using only straight edge and compass
Construction 18 – Angle of 60⁰ without using a protractor or set square
Construction 19 – Tangent to a given circle at a given point on it
Construction 20 – Parallelogram, given the length of the sides and the measure of the angles
Construction 21 – Centroid of a triangle
See below for our demonstration videos showing you exactly how to do them.
If you need any further help or clarification, get in touch with us at any time!
All 19 Constructions for Leaving Cert Ordinary Level
Full Playlist – all 19 videos on our YouTube channel
Construction 1 – Bisector of an angle, using only compass and straight edge
Construction 2 – Perpendicular bisector of a segment, using only compass and straight edge
Construction 4 – Line perpendicular to a given line l, passing through a given point on l
Construction 5 – Line parallel to given line, through a given point
Construction 6 and 7 – Division of a line into 2, 3 or any number of equal segments without measuring it [7 Not on Ordinary Level]
Construction 8 – Line segment of a given length on a given ray
Construction 9 – Angle of a given number of degrees with a given ray as one arm
Construction 10 – Triangle, given lengths of 3 sides
Construction 11 – Triangle, given SAS data
Construction 12 – Triangle, given ASA data
Construction 13 – Right-angled triangle, given length of hypotenuse and one other side
Construction 14 – Right-angled triangle, given one side and one of the acute angles
Construction 15 – Rectangle given side lengths
Construction 16 – To construct the circumcentre and circumcircle of a given triangle.
Construction 17 – To construct the in-centre and in-circle of a given triangle.
Construction 18 – Use this interactive file to construct an angle of 60 degrees.
Construction 19 – Use this file to learn to construct the tangent to a circle at a given point on it.
Construction 20 – Use this file to learn to construct a parallelogram, given the length of sides and the measure of the angles.
Construction 21 – Use this file to learn to construct the centroid of a triangle.