For now, I will only post pictures of the theorems. Perhaps later I will add links that talk about the theorems in detail
Potema's theorem:
Two squares created on the sides of a triangle $∆ABC$ And we set the point $M$ Which represents the middle $EF$ It will be constant no matter how you move point $C$ As long as $A,B$ are constant
Fensler-Hadwiger theorem
We have two squares with a common vertex between them, so they will be the midpoints of the spaces between the opposite vertices, and the centers of the two squares will form the vertices of a third square
Two squares with a common vertex, the previous three properties will be fulfilled
If two squares have a common vertex, the two red lines will be perpendicular and equal
If we have two identical squares with one vertex at the center of the other, the common area between the two squares will be equal to a quarter of the area of one square
In the previous figure there are two properties achieved:
The first is that $AM=BM$
The second characteristic is that $PQ=2MN$
Two identical or different squares intersect and are enclosed between them $A,B,C,D$ The aforementioned equality will be achieved
If two identical or different squares have a common vertex, the blue area will be equal to the red area
If two squares have a common vertex, these three lines will meet at one point
Moreover, the circles of the two squares pass through the same point, which represents the center of the spiral similarity
If two squares have parallel sides, these lines will meet at one point
Furthermore itIf the two squares do not have parallel sides, then these lines will meet at one point.
In the previous figure it would be: $\frac{b}{a}=\frac{\sqrt{5}+1}{2}=Φ$
In the previous picture it is:
$X=\frac{5(A-B)}{8}$
We have two squares that have a common vertex, the point $F$ moves freely along the straight line $CD$ It will be points $A,C,Q$ Located on one straight line
Two squares in the plane In the general case, these two lines will be perpendicular
Here are some theorems that can be understood from pictures only without words: