catatomic
Gold Member
- Nov 28, 2012
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Previous attempt I just proved the pythagorean theorem
In fig. 1, x is defined so that ax+ax+x2 = b2, and in fig. 2 y is defined so that by+by+y2=a2.
Fig. 1 and Fig. 2 have the same area a2+b2, and they are square, so they have the same edges in each and together. a2+02=c2 and 02+02=02 are trivial. The edges are all a+x or b+y.
Fig. 3 and 4 suggest c=a+x and c=b+y.
c will fit in the square because a and b fit in the square (fig. 5). WLOG (without loss of generality) c can connect edges. We can connect adjacent edges like fig. 6, have an edge like fig. 7, or connect opposite edges like fig. 8. In the case of figure 6 we can have those edges be a and b.
In fig. 6 we want each triangle to be a and b and to be the same size so it stretches around perfectly. Note that c2 < the total square area. This means that c2 < a2 + b2 but we need to prove that impossible. See fig. 9. BC will be y. GH will be x so that CD will be x. So BC= a and y and CD = b and x. Note that x2 < b2 and y2 < a2 so that x2+y2 < a2+b2 but they are also equal. a2+b2 < a2 + b2, a contradiction. Then c2 is not less than a2+b2.
Next we try fig. 10. This time it stretches past the length of an edge of the big square. One side will be a+x and b+y, so it will be bigger than a and bigger than b. That means we donāt have to consider it since it cannot be a and b.
What if we bend that c to fit on adjacent sides?
Using fig. 9,we have the same problem. So c2 is not greater than a2+b2. We can also try to bend a c that fits two adjacent sides to across and then the problem with going across occurs.
Then c2 is not greater than a2+b2
The only thing left is that c is a side of the big square or parallel to it.
c2 = a2+b2 or if we look at (a+x)2 and (b+y)2 together we also get 2c2 = 2a2+2b2. It will look like figs. 11 and 12. Note that in fig. 12 it wonāt be the same as like fig. 9 (it wonāt stretch around evenly).
In fig. 1, x is defined so that ax+ax+x2 = b2, and in fig. 2 y is defined so that by+by+y2=a2.
Fig. 1 and Fig. 2 have the same area a2+b2, and they are square, so they have the same edges in each and together. a2+02=c2 and 02+02=02 are trivial. The edges are all a+x or b+y.
Fig. 3 and 4 suggest c=a+x and c=b+y.
c will fit in the square because a and b fit in the square (fig. 5). WLOG (without loss of generality) c can connect edges. We can connect adjacent edges like fig. 6, have an edge like fig. 7, or connect opposite edges like fig. 8. In the case of figure 6 we can have those edges be a and b.
In fig. 6 we want each triangle to be a and b and to be the same size so it stretches around perfectly. Note that c2 < the total square area. This means that c2 < a2 + b2 but we need to prove that impossible. See fig. 9. BC will be y. GH will be x so that CD will be x. So BC= a and y and CD = b and x. Note that x2 < b2 and y2 < a2 so that x2+y2 < a2+b2 but they are also equal. a2+b2 < a2 + b2, a contradiction. Then c2 is not less than a2+b2.
Next we try fig. 10. This time it stretches past the length of an edge of the big square. One side will be a+x and b+y, so it will be bigger than a and bigger than b. That means we donāt have to consider it since it cannot be a and b.
What if we bend that c to fit on adjacent sides?
Using fig. 9,we have the same problem. So c2 is not greater than a2+b2. We can also try to bend a c that fits two adjacent sides to across and then the problem with going across occurs.
Then c2 is not greater than a2+b2
The only thing left is that c is a side of the big square or parallel to it.
c2 = a2+b2 or if we look at (a+x)2 and (b+y)2 together we also get 2c2 = 2a2+2b2. It will look like figs. 11 and 12. Note that in fig. 12 it wonāt be the same as like fig. 9 (it wonāt stretch around evenly).