[] , [] , [^] , []Adding feet of perpendiculars to triangle / Bonus?(GC World : Various Problems ,What will occur when something is added?)
Let's observe this figure after you have some conjecture that certain shape is similar to ABC.
Or let's make the following figure by moving points.
You may find "it became so at this time".
You can see a new relationship by comparing this with other figures even if you didn't have any interest at the beginning.
I think this is worth "bonus points".


Forum of Geometric Constructor by Y.Iijima