Draw a perpendicular segment from the incenter to one of the triangle's sides. *
Ben botched the second step. Once we have found the point of intersection between the perpendicular segment and the triangle's side, we can draw the inscribed circle by opening up our compass until its width equals the distance between the incenter and the intersection.
Drawing the Perpendicular Line
To draw the perpendicular line, place the needle point of the compass at the incenter and draw an arc that intersects one of the triangle's sides at two points.
Next, use the intersection points to draw a pair of intersecting arcs as shown below.
Finally, use a straightedge to draw a segment from the incenter to the intersection of the pair of arcs. This segment is perpendicular to AB.
Drawing the inscribed circle
Now open up the compass so that it is as wide as the distance between the incenter and the point of intersection between AB and the perpendicular segment. This will allow us to draw the inscribed circle.
