Theorem s7len

Description: The length of a length 7 string. (Contributed by Mario Carneiro, 26-Feb-2016)

	Ref	Expression
Assertion	s7len	$$⊢\left|⟨“ABCDEFG”⟩\right|=7$$

Proof

Step	Hyp	Ref	Expression
1		df-s7	$$⊢⟨“ABCDEFG”⟩=⟨“ABCDEF”⟩\mathrm{++}⟨“G”⟩$$
2		s6cli	$$⊢⟨“ABCDEF”⟩\in \mathrm{Word}\mathrm{V}$$
3		s6len	$$⊢\left|⟨“ABCDEF”⟩\right|=6$$
4		6p1e7	$$⊢6+1=7$$
5	1 2 3 4	cats1len	$$⊢\left|⟨“ABCDEFG”⟩\right|=7$$