Two lines are perpendicular if and only if they form right angles at their point of intersection. Step-by-step directions for constructing a line perpendicular to a segment are described below. Try using your compass and straightedge to construct the angle as you follow along with the directions.
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Start with a line and point K on that line.
Set the compass's width to a medium setting. The actual width does not matter.
Without changing the compass's width, mark a short arc on the line at each side of the point K, forming the points P and Q. These two points are the same distance from K because you did not change the width of the compass.
Increase the compass to almost double the width (the exact setting is not important).
From P, mark off a short arc above K
Without changing the compass's width, repeat from the point Q so that the two arcs cross each other, creating the point R
Using the straight edge, draw a line from K to where the arcs cross. |
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To see an animation of the construction, click the play button below. This animation does not include audio - it only shows each step as it occurs in the correct order.
