Use the compass and the parallel line tools to make triangles.
Always put one side of your triangle on the dotted line.

a

b

c

A = (-3.78, 5.88)
a = OrthogonalLine(A, yAxis)
B = (-3.84, 5.24)
b = OrthogonalLine(B, yAxis)
C = (-3.84, 4.66)
c = OrthogonalLine(C, yAxis)
D = Point(a)
d = Segment(A, D)
E = Point(b)
e = Segment(B, E)
F = Point(c)
f = Segment(C, F)
G = (1.5, 5.14)
g = OrthogonalLine(G, yAxis)
H = (4.78, 5.14)
h = OrthogonalLine(H, yAxis)
I = Point(g)
k = Semicircle(G, I)
J = Point(h)
p = Semicircle(H, J)
K = Center(k)
M = Point(p)
N = Point(k)
β = Angle(I, K, N)
l = Segment(I, K)
m = Segment(K, N)
L = Center(p)
α = Angle(M, L, H)
i = Segment(L, H)
j = Segment(L, M)
O = (-0.94, -1.34)
n = Line(O, f)
o = Distance(e, f)