Trisecting a LineDate: 11/03/97 at 17:38:08 From: megan federow Subject: Trisecting a line How would you trisect a line using a compass and a straight edge? I tried with circles but i don't know if that is right. Could you help me? Thanks. Date: 11/03/97 at 19:21:33 From: Doctor Tom Subject: Re: Trisecting a line Hi Megan, The usual construction is this: Draw another line that goes through one of the endpoints of the segment that you're trying to trisect. In reality, it can be any line, but it works best if it makes a relatively small angle (say 30 degrees) with the original segment. Next, open your compass to any size (but it works better if the size is roughly 1/3 of the size of the segment you're trying to trisect). Put the point of the compass on the intersection of the segment and your new line, and make a mark on the new line with the pencil on the compass. Now put the point of the compass at that new mark (without changing the opening), and mark another point on the new line. Do it again, and you'll have three equal-sized segments marked off on the new line. From the final mark, draw a line to the other end of the segment you're trying to trisect. Then construct lines parallel to that one going through the other two new points on the line. These three parallel lines will trisect the original segment. This would sure be easier to explain with a drawing! -Doctor Tom, The Math Forum Check out our web site! http://mathforum.org/dr.math/ |
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