Theorem s4s2

Description: Concatenation of fixed length strings. (Contributed by Mario Carneiro, 26-Feb-2016)

	Ref	Expression
Assertion	s4s2	|- <" A B C D E F "> = ( <" A B C D "> ++ <" E F "> )

Proof

Step	Hyp	Ref	Expression
1		df-s2	|- <" E F "> = ( <" E "> ++ <" F "> )
2		s4cli	|- <" A B C D "> e. Word _V
3		s1cli	|- <" E "> e. Word _V
4		df-s6	|- <" A B C D E F "> = ( <" A B C D E "> ++ <" F "> )
5		df-s5	|- <" A B C D E "> = ( <" A B C D "> ++ <" E "> )
6	1 2 3 4 5	cats1cat	|- <" A B C D E F "> = ( <" A B C D "> ++ <" E F "> )