Isosceles triangle given base and altitude
Geometry construction using a compass and straightedge

How to draw an isosceles triangle given the base and altitude with compass and straightedge or ruler. The base is the unequal side of the triangle and the altitude is the perpendicular height from the base to the apex. It works by first copying the base segment, then constructing its perpendicular bisector. The apex is then marked up from the base.

Printable step-by-step instructions

The above animation is available as a printable step-by-step instruction sheet, which can be used for making handouts or when a computer is not available.

Try it yourself

Click here for a printable isosceles construction worksheet containing two problems to try. When you get to the page, use the browser print command to print as many as you wish. The printed output is not copyright.

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Non-Euclidean constructions