Lemma 13.2.
Assuming that:
E
,
E
′
are
elliptic curves
over
ℚ
ϕ
:
E
→
E
′
an
isogeny
defined over
ℚ
Then
there exists
c
>
0
such that
|
h
(
ϕ
(
P
)
)
−
(
deg
ϕ
)
h
(
P
)
|
≤
c
∀
P
∈
E
(
ℚ
)
.