My image has all informations!

In fact the solution will be to draw a line from any red point and cut the 2 sides of the black angle
on B & C with the exact length of the segment A. (red A' = A)

Alas geometric tools given by Moi today are not sufficient for make that!

Of course black segment A and red point on the left can be any thing reasonnable!

Tool is asked! :)

For this red point and this black segment that is evident !
but for another red Point with same segment? Or / and another segment? .... ;)