a_2(y) = y < 0
A_2 = Point(a_2)
B_1 = Point(xAxis)
α = 0.7155849933176751 rad (slider from 0 to 180°)
B' = Rotate(B_1, α, A_2)
β = Angle(B_1, A_2, B')
f = Ray(A_2, B')
A = (8.212671327750543, 3.3375287325940084)
A_1 = Mirror(A, f)
A'_1 = Mirror(A, xAxis)
g = Segment(A_1, A'_1)
B = Intersect(g, f)
C = Intersect(g, xAxis)
t1, c, a, b = Polygon(A, B, C)
Ümbermõõt: a + b + c
text1: "Kolmnurga ABC Ümbermõõt = " + Ümbermõõt + ""