Trisect A Line With a Compass, Straight Edge, And Marking Device

# Thread: Trisect A Line With a Compass, Straight Edge, And Marking Device

1. ## Trisect A Line With a Compass, Straight Edge, And Marking Device

This is pretty cool you can actually trisect a line with just a compass and a straight edge. It was in an old book I had, I mean like really old.

You just swing two arcs up to form the large triangle, then bisect the sides and you have the center point, then just swing two arcs the length of the midpoint of the height of the will be little triangle and get a thirty degree side of the smaller triangle. It is pretty cool, all you need is a compass and a straight edge or even a string, and of course a marking device.

I have some others for making circles inside of circles pretty cool stuff.

Sincerely,

William McCormick

2. ## Re: Trisect A Line With a Compass, Straight Edge, And Marking Device

This is pretty easy but cool.

Sincerely,

William McCormick

3. ## Re: Trisect A Line With a Compass, Straight Edge, And Marking Device

This is six circles in a cirlcle. All these are done without a tape measure or protractor.

Sincerely,

William McCormick

4. ## Re: Trisect A Line With a Compass, Straight Edge, And Marking Device

Dave, would you concur? That it can be done with just a compass/dividers, a string or straight edge, and a marking device?

You would not even need a square.

Sincerely,

William McCormick

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## Re: Trisect A Line With a Compass, Straight Edge, And Marking Device

That is interesting. in the first sketch, It is also a pictorial/proof representation of how/why you can take a line/rule of known length/division(blue) and divide a line of unknown length (Green).

Even shows similar triangles and how the divide the green line.

Lots of ways to torture young geometry students and have parent calling admin claiming irrelevance.

6. ## Re: Trisect A Line With a Compass, Straight Edge, And Marking Device

Originally Posted by tapwelder
That is interesting. in the first sketch, It is also a pictorial/proof representation of how/why you can take a line/rule of known length/division(blue) and divide a line of unknown length (Green).

Even shows similar triangles and how the divide the green line.

Lots of ways to torture young geometry students and have parent calling admin claiming irrelevance.
Oh yea you can just use the old variable increment on an angle and do the same. But I thought that was pretty cool.

Sincerely,

William McCormick

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