How to construct a square equal to a given triangle.

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I have a triangle $ABC$ and I want to construct a square of the same area as that of the triangle using ruler and compass.



Consider the following image.



I first locate the mid-points of $AB$ and $BC$ and draw a line parallel to $AB$ passing through $C$. Say this line intersects $PQ$ at $A'$. Then chopping off $APQ$ and putting it in place of $A'QC$ leads to the parallelogram $PA'CB$.



Dropping perpendiculars from $P$ and $A'$ to $BC$ gives points $R$ and $B'$. Chopping off the triangle $PBR$ from the paralellogram and sliding it to coincide with the imaginary triangle $A'CB'$ leads to the rectangle $PRB'A'$.



Now I want to convert this rectangle into a square. I could do something like Job Bouwman's answer here but that construction does not have the spirit of "chopping off and rearranging the pieces to obtain a square".



Can somebody see as to how to go about hacking away at the rectangle and make the pieces fall into the shape of a square?



Thank you.










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  • Start with the rectangle that you have. I like this construction of quadrature of the rectangle based on Euclid's theorem, but it does not give a cut-and-rearrange the pieces method serge.mehl.free.fr/exos/quadra_rect.html
    – user376343
    1 hour ago















up vote
5
down vote

favorite
2












I have a triangle $ABC$ and I want to construct a square of the same area as that of the triangle using ruler and compass.



Consider the following image.



I first locate the mid-points of $AB$ and $BC$ and draw a line parallel to $AB$ passing through $C$. Say this line intersects $PQ$ at $A'$. Then chopping off $APQ$ and putting it in place of $A'QC$ leads to the parallelogram $PA'CB$.



Dropping perpendiculars from $P$ and $A'$ to $BC$ gives points $R$ and $B'$. Chopping off the triangle $PBR$ from the paralellogram and sliding it to coincide with the imaginary triangle $A'CB'$ leads to the rectangle $PRB'A'$.



Now I want to convert this rectangle into a square. I could do something like Job Bouwman's answer here but that construction does not have the spirit of "chopping off and rearranging the pieces to obtain a square".



Can somebody see as to how to go about hacking away at the rectangle and make the pieces fall into the shape of a square?



Thank you.










share|cite|improve this question























  • Start with the rectangle that you have. I like this construction of quadrature of the rectangle based on Euclid's theorem, but it does not give a cut-and-rearrange the pieces method serge.mehl.free.fr/exos/quadra_rect.html
    – user376343
    1 hour ago













up vote
5
down vote

favorite
2









up vote
5
down vote

favorite
2






2





I have a triangle $ABC$ and I want to construct a square of the same area as that of the triangle using ruler and compass.



Consider the following image.



I first locate the mid-points of $AB$ and $BC$ and draw a line parallel to $AB$ passing through $C$. Say this line intersects $PQ$ at $A'$. Then chopping off $APQ$ and putting it in place of $A'QC$ leads to the parallelogram $PA'CB$.



Dropping perpendiculars from $P$ and $A'$ to $BC$ gives points $R$ and $B'$. Chopping off the triangle $PBR$ from the paralellogram and sliding it to coincide with the imaginary triangle $A'CB'$ leads to the rectangle $PRB'A'$.



Now I want to convert this rectangle into a square. I could do something like Job Bouwman's answer here but that construction does not have the spirit of "chopping off and rearranging the pieces to obtain a square".



Can somebody see as to how to go about hacking away at the rectangle and make the pieces fall into the shape of a square?



Thank you.










share|cite|improve this question















I have a triangle $ABC$ and I want to construct a square of the same area as that of the triangle using ruler and compass.



Consider the following image.



I first locate the mid-points of $AB$ and $BC$ and draw a line parallel to $AB$ passing through $C$. Say this line intersects $PQ$ at $A'$. Then chopping off $APQ$ and putting it in place of $A'QC$ leads to the parallelogram $PA'CB$.



Dropping perpendiculars from $P$ and $A'$ to $BC$ gives points $R$ and $B'$. Chopping off the triangle $PBR$ from the paralellogram and sliding it to coincide with the imaginary triangle $A'CB'$ leads to the rectangle $PRB'A'$.



Now I want to convert this rectangle into a square. I could do something like Job Bouwman's answer here but that construction does not have the spirit of "chopping off and rearranging the pieces to obtain a square".



Can somebody see as to how to go about hacking away at the rectangle and make the pieces fall into the shape of a square?



Thank you.







geometry geometric-construction






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edited 47 mins ago









Parcly Taxel

34.3k136890




34.3k136890










asked 1 hour ago









caffeinemachine

6,25021146




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  • Start with the rectangle that you have. I like this construction of quadrature of the rectangle based on Euclid's theorem, but it does not give a cut-and-rearrange the pieces method serge.mehl.free.fr/exos/quadra_rect.html
    – user376343
    1 hour ago

















  • Start with the rectangle that you have. I like this construction of quadrature of the rectangle based on Euclid's theorem, but it does not give a cut-and-rearrange the pieces method serge.mehl.free.fr/exos/quadra_rect.html
    – user376343
    1 hour ago
















Start with the rectangle that you have. I like this construction of quadrature of the rectangle based on Euclid's theorem, but it does not give a cut-and-rearrange the pieces method serge.mehl.free.fr/exos/quadra_rect.html
– user376343
1 hour ago





Start with the rectangle that you have. I like this construction of quadrature of the rectangle based on Euclid's theorem, but it does not give a cut-and-rearrange the pieces method serge.mehl.free.fr/exos/quadra_rect.html
– user376343
1 hour ago











1 Answer
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up vote
4
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Given a rectangle with side lengths $a,b$ we want to construct a square of the same area. Without loss of generality assume $a>b$.



The first step is to obtain the square's side length $m=sqrtab$. This is a classical construction; erect a semicircle on a segment of length $a+b$ and draw the perpendicular from a point $a$ from one end. The length of that perpendicular within the semicircle is $m$.



The actual cuts to the rectangle that transform it into a square are based off a 2016 paper on illustrating the Bolyai–Gerwien theorem. From one vertex draw a cut to the long opposite side, creating a right triangle with legs $m$ and $b$. On the long side incident to said vertex, erect a perpendicular cut at the point $a-m$ from the vertex that stops at the first cut (this second cut has length $m-b$). This creates three pieces, which rearrange into a square, as shown above.



If $a>4b$, the above construction will not work. In this case, repeatedly bisect the rectangle parallel to its short side and stack the halves on top of each other until $ale4b$.






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  • Great. This is what I was looking for. I'll wait for some time and then accept.
    – caffeinemachine
    16 mins ago










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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes








up vote
4
down vote















Given a rectangle with side lengths $a,b$ we want to construct a square of the same area. Without loss of generality assume $a>b$.



The first step is to obtain the square's side length $m=sqrtab$. This is a classical construction; erect a semicircle on a segment of length $a+b$ and draw the perpendicular from a point $a$ from one end. The length of that perpendicular within the semicircle is $m$.



The actual cuts to the rectangle that transform it into a square are based off a 2016 paper on illustrating the Bolyai–Gerwien theorem. From one vertex draw a cut to the long opposite side, creating a right triangle with legs $m$ and $b$. On the long side incident to said vertex, erect a perpendicular cut at the point $a-m$ from the vertex that stops at the first cut (this second cut has length $m-b$). This creates three pieces, which rearrange into a square, as shown above.



If $a>4b$, the above construction will not work. In this case, repeatedly bisect the rectangle parallel to its short side and stack the halves on top of each other until $ale4b$.






share|cite|improve this answer






















  • Great. This is what I was looking for. I'll wait for some time and then accept.
    – caffeinemachine
    16 mins ago














up vote
4
down vote















Given a rectangle with side lengths $a,b$ we want to construct a square of the same area. Without loss of generality assume $a>b$.



The first step is to obtain the square's side length $m=sqrtab$. This is a classical construction; erect a semicircle on a segment of length $a+b$ and draw the perpendicular from a point $a$ from one end. The length of that perpendicular within the semicircle is $m$.



The actual cuts to the rectangle that transform it into a square are based off a 2016 paper on illustrating the Bolyai–Gerwien theorem. From one vertex draw a cut to the long opposite side, creating a right triangle with legs $m$ and $b$. On the long side incident to said vertex, erect a perpendicular cut at the point $a-m$ from the vertex that stops at the first cut (this second cut has length $m-b$). This creates three pieces, which rearrange into a square, as shown above.



If $a>4b$, the above construction will not work. In this case, repeatedly bisect the rectangle parallel to its short side and stack the halves on top of each other until $ale4b$.






share|cite|improve this answer






















  • Great. This is what I was looking for. I'll wait for some time and then accept.
    – caffeinemachine
    16 mins ago












up vote
4
down vote










up vote
4
down vote











Given a rectangle with side lengths $a,b$ we want to construct a square of the same area. Without loss of generality assume $a>b$.



The first step is to obtain the square's side length $m=sqrtab$. This is a classical construction; erect a semicircle on a segment of length $a+b$ and draw the perpendicular from a point $a$ from one end. The length of that perpendicular within the semicircle is $m$.



The actual cuts to the rectangle that transform it into a square are based off a 2016 paper on illustrating the Bolyai–Gerwien theorem. From one vertex draw a cut to the long opposite side, creating a right triangle with legs $m$ and $b$. On the long side incident to said vertex, erect a perpendicular cut at the point $a-m$ from the vertex that stops at the first cut (this second cut has length $m-b$). This creates three pieces, which rearrange into a square, as shown above.



If $a>4b$, the above construction will not work. In this case, repeatedly bisect the rectangle parallel to its short side and stack the halves on top of each other until $ale4b$.






share|cite|improve this answer
















Given a rectangle with side lengths $a,b$ we want to construct a square of the same area. Without loss of generality assume $a>b$.



The first step is to obtain the square's side length $m=sqrtab$. This is a classical construction; erect a semicircle on a segment of length $a+b$ and draw the perpendicular from a point $a$ from one end. The length of that perpendicular within the semicircle is $m$.



The actual cuts to the rectangle that transform it into a square are based off a 2016 paper on illustrating the Bolyai–Gerwien theorem. From one vertex draw a cut to the long opposite side, creating a right triangle with legs $m$ and $b$. On the long side incident to said vertex, erect a perpendicular cut at the point $a-m$ from the vertex that stops at the first cut (this second cut has length $m-b$). This creates three pieces, which rearrange into a square, as shown above.



If $a>4b$, the above construction will not work. In this case, repeatedly bisect the rectangle parallel to its short side and stack the halves on top of each other until $ale4b$.







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited 6 mins ago

























answered 52 mins ago









Parcly Taxel

34.3k136890




34.3k136890











  • Great. This is what I was looking for. I'll wait for some time and then accept.
    – caffeinemachine
    16 mins ago
















  • Great. This is what I was looking for. I'll wait for some time and then accept.
    – caffeinemachine
    16 mins ago















Great. This is what I was looking for. I'll wait for some time and then accept.
– caffeinemachine
16 mins ago




Great. This is what I was looking for. I'll wait for some time and then accept.
– caffeinemachine
16 mins ago

















 

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