be the ring of continuous functions on [0,1].
→ ℝ by

Proof. The map φ preserves the operations of addition and multiplication due to

and

Furthermore the additive and multiplicative identities of
are mapped to the additive and multiplicative
identities of ℝ:

and

__
With this definition of φ, we have that the kernel is exactly I = {f ∈
| f(c) = 0}. Hence with the above lemma, I
is an ideal of
. Futhermore, due to the above lemma and because φ is surjective (for a ∈ [0,1], the map x
a is
mapped to a by φ), the Fundamental Theorem of Ring Homomorphisms implies that
∕I is isomorphic to ℝ since ℝ
is a field, this implies that the ideal I is a maximal ideal.