Step-by-step Instructions

After doing this	Your work should look like this
Start with three line segments that will be the three sides of the triangle ABC.
1.  Mark a point A that will be one vertex of the new triangle.
2.  Set the compass width to the length of the segment AB. This will become the base of the new triangle.
3.  With the compass point on A, make an arc near the future vertex B of the triangle.
4.  Mark a point B on this arc. This will become the next vertex of the new triangle.
5.  Set the compass width to the length of the line segment AC.
6.  Place the compass point on A and make an arc in the vicinity of where the third vertex of the triangle (C) will be. All points along this arc are the distance AC from A, but we do not yet quite know exactly where the vertex C is.
7.  Use the compass to measure the length of the segment BC, the length of the third side of the triangle.
8.  From point B, draw an arc crossing the first. Where these intersect is the vertex C of the triangle
9.  Finally, draw the three sides AB, AC, and BC of the new triangle.
10.  Done. The blue triangle ABC has each side congruent to the the corresponding line segment.

Constructions pages on this site

Lines

• Introduction to constructions
• List of printable constructions worksheets
• Copy a line segment
• Parallel line through a point
• Perpendicular bisector of a line segment
• Perpendicular from a line at a point
• Perpendicular from a line through a point
• Perpendicular from endpoint of a ray
• Divide a segment into n equal parts

Angles

• Bisecting an angle
• Copy an angle
• Construct a 30° angle
• Construct a 45° angle
• Construct a 60° angle
• Construct a 90° angle (right angle)
• Constructing  75°  105°  120°  135°  150° angles and more

Triangles

• Copy a triangle
• Isosceles triangle, given base and side
• Isosceles triangle, given base and altitude
• Equilateral triangle
• Triangle medians
• 30-60-90 triangle, given the hypotenuse
• Triangle, given 3 sides (sss)
• Triangle, given one side and adjacent angles (asa)
• Triangle, given two sides and included angle (sas)
• Incircle of a triangle
• Circumcircle of a triangle

Triangle Centers

• Triangle incenter
• Triangle circumcenter
• Triangle orthocenter
• Triangle centroid

Circles, Arcs and Ellipses

• Finding the center of a circle
• Circle given 3 points
• Tangent at a point on the circle
• Tangents through an external point
• Focus points of a given ellipse

Non-Euclidean constructions

• Construct an ellipse with string and pins
• Find the center of a circle with any right-angled object