tranquil arc is incorrectly written and it should be written as "quiet arc" being its meaning: tranquil arch = arch tranquil known also by the names of Red bow or gooseneck and also by botarel. It is an asymmetrical ellipsoidal with inclined starts line, i.e., with starting points at different level, generally used in buttresses and stairs. It is usually traced through several arches of circumference. The simplest layout with only two centres, is carried out as follows: the light and the arrow 1-2, rises about 1 the perpendicular bisector of the line a-b boot. Then stand perpendicular bisectors on the straight A-2 and 2-B, which, of course, will also pass through the Center 1 and cut the horizontal drawn from A and B, respectively, in paragraphs 3 and 4. These are the centers of the arches of circumference A-2 and 2-B, tangent each other in 2, forming the arch TRANQUIL sought.