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Constructing an isosceles triangle with compass and straight-edge

Draw a line segment and mark two points on it:

Now, set your compass to a length greater than half the distance between the two points. Put the compass point on one of the two points you marked on the line and draw an arc that goes across the midpoint of the line segment defined by your two points:

Putting the point of your compass on the other point, draw another arc, so that you have two intersecting arcs:

Draw a line segment connecting one of your two points to the intersection of the arcs:

Then draw a second line segment connecting the other point to the intersection of the arcs:

You now have an isosceles triangle.

Last updated 26 Feb 2006.   Send me an e-mail.