r

a=arco AB

r_1 = 2.1 (slider from 0.2 to 5, step 0.1)
C = (2.78, 2.38)
c = Circle(C, r_1)
B = Point(c)
a_1 = Ray(C, B)
A = Point(c)
b = Ray(C, A)
a = CircleArc(C, B, A)
r = Segment(C, B)
e = Segment(C, A)
θ = Angle(B, C, A)
d: a / r
f = CircleSector(C, B, A)
texto2: "amplitude\ de\ \theta\ em\ radianos = 
\displaystyle\frac{arco \ AB} {raio \ r}=\displaystyle\frac{" + (LaTeX[a]) + "} {" + (LaTeX[r]) + "}=" + (LaTeX[d]) + "\ rad"
texto1: "amplitude\ de\  \theta \ em \ graus =" + (LaTeX[θ]) + ""