
Copying a Triangle
Geometry construction using a compass and straightedge
Given a triangle, this page shows how to construct another triangle that is
congruent
to it using a compass and straightedge or ruler.
Printable stepbystep instructions
The above animation is available as a
printable stepbystep instruction sheet, which can be used for making handouts
or when a computer is not available.
Proof
The image below is the final drawing above.

Argument 
Reason 
1 
PR is
congruent to (same length as) AC 
PR drawn with compass width set from AC 
2 
RQ is
congruent to (same length as) CB 
RQ drawn with compass width set from CB 
3 
PQ is
congruent to (same length as) AB 
PQ drawn with compass width set from AB 
4 
Triangles ABC, PQR are congruent (same shape and size) 
Congruence rule SSS  three sides congruent 
5 
Triangle PRQ is an exact copy of triangle ABC 
From (4) 
 Q.E.D
Try it yourself
Click here for a printable worksheet containing two triangle copying problems.
When you get to the page, use the browser print command to print as many as you wish. The printed output is not copyright.
Constructions pages on this site
Lines
Angles
Triangles
Right triangles
Triangle Centers
Circles, Arcs and Ellipses
Polygons
NonEuclidean constructions
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