Is there any method or library abstraction in order to draw an arc or a half-circle by ordering the strarting and finishing angle degrees or sth like this, in Gem?

Answer my question:
Mathimaticaly, draw a cubic bezier curve [curve 4]
Use this link ( http://itc.ktu.lt/itc354/Riskus354.pdf ) to read how to find the points.

Later i 'll attach an abstraction the sooner i optimize it, but doing it by paper and pencil you save ram and time by calculation lots of things..