n

a_n

a(n) = 20 - n
N = 50
indice = Sequence((n, 0), n, 1, N)
termos = Sequence((n, a(n)), n, 1, N)
n_1 = Point(xAxis)
n: x(n_1)
A: (0, a(n))
a_n: y(A)
c = OrthogonalLine(n_1, xAxis)
d = OrthogonalLine(A, yAxis)
B = Intersect(d, c)
e = Segment(n_1, B)
f = Segment(B, A)