

Isosceles Triangle given the leg length and apex angle
Geometry construction using a compass and straightedge
This construction produces an
isosceles triangle given the length of the legs and the apex angle (the one at the top). The
construction proceeds in two main steps:
 Copy the angle, making sure each leg of the angle is longer than the desired side length of the triangle. This is exactly the same
as the construction
Copying an angle with compass and straightedge.
 Mark off the length of the two legs of the triangle and draw the base line.
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
 Q.E.D
Try it yourself
Click here for a printable worksheet containing two triangle construction 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.
Other constructions pages on this site
Lines
Angles
Triangles
Right triangles
Triangle Centers
Circles, Arcs and Ellipses
Polygons
NonEuclidean constructions
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