Let x be given.

Assume Hx: x ∈ complex.

We will prove x ∈ quaternion.

rewrite the current goal using CSNo_pair_0 x (from right to left).

We will prove pa x 0 ∈ quaternion.

Apply quaternion_I to the current goal.

An exact proof term for the current goal is Hx.

An exact proof term for the current goal is complex_0.

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