x_0

x_0+h

f(x_0)

f(x_0+h)

\begin{tabular}{l}
\overline{DK}=1\
\alpha=K\hat{D}L\
\beta=K\hat{D}M\
\overline{KL}=\tan(\alpha)=\frac{f(x_0+h)-f(x_0}{h}\
\overline{KM}=\tan(\beta)=f'(x_0)
\end{tabular}

U = (8, 0)
A = (2.3, 0)
a = OrthogonalLine(A, xAxis)
B = Intersect(a, xAxis)
l = Segment(B, U)
f(x) = 2 log(x - 1) + 1
C = Point(l)
b = OrthogonalLine(C, xAxis)
D = Intersect(f, a, (2.3, 1.5247285289349817))
E = Intersect(f, b, (7.3, 4.681099266794973))
c = OrthogonalLine(D, a)
F = Intersect(c, b)
d = OrthogonalLine(E, b)
G = Intersect(c, yAxis)
H = Intersect(d, yAxis)
e = Line(D, E)
g = Tangent(D, f)
M_1: (x(A) + 1, 0)
h = OrthogonalLine(M_1, xAxis)
L = Intersect(e, h)
M = Intersect(g, h)
u = Vector(B, D)
v = Vector(D, G)
w = Vector(C, E)
z = Vector(E, H)
K = Intersect(c, h)
i = Segment(D, F)
j = Segment(K, L)
k = Segment(L, M)
L_1 = Point(i)
N = Point(i)
p = CircleArc(D, L_1, L)
q = CircleArc(D, N, M)
O = Point(xAxis)
P = Point(xAxis)
m = Vector(O, P)
Q = Point(yAxis)
R = Point(yAxis)
n = Vector(Q, R)