
Proof of t he Maximum Principle 225
and let
λ(ε, t) =
¯
λ(ε, t)/M(ε). (7.6.9)
We now divide through by M (ε) in (7.6 .7) and use (7.6.9) to get
λ
′
(ε, t) = M(ε)
−1
f
0
x
(ε, t) −f
x
(ε, t)
T
λ(ε, t) + 2M (ε)
−1
f
x
(ε, t)
T
(ψ
′
ε
(t) −ψ
′
x
(t)).
(7.6.10)
In summary, we have shown that since ψ
ε
minimizes (7.6.1 ) over T
ε/2
(ψ
∗
),
there exists an absolutely continuous function λ(ε, ·) such that (7.6.10) holds
a.e. on [0, 1].
Since ψ
ε
minimizes (7.6.1) over T
ε/2
(ψ
∗
), the transversality condition
(7.4.9) of Lemma 7.4 .8 holds. We suppose the e(ψ
ε
) is an interior point of
B. From the first equation in (7.6.2) we get tha t
γ
x
0
(e(ψ
ε
)) = g
x
0
(e(ψ
ε
)) + 2(ψ
ε
(0) − ψ
∗
(0))
γ
x
1
(e(ψ
ε
)) = g
x
1
(e(