The pointed arch has three shapes (see picture from Wikipedia):
1. lancet arch (arc brisé en lancette)
2. equilateral pointed arch (arc brisé en tiers-point)
3. lowered pointed arc
In case of a lancet arch the centre of both arcs lies outside the lancet arch.
The equilateral pointed arch is an arch based on an equilateral triangle; the centres of the arcs with radii R1 and R2 are M1 and M2.
See also arc ogival and arc brisé.
|Lancette - Wikipedia|