Theorem s4s3

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

	Ref	Expression
Assertion	s4s3	|- <" A B C D E F G "> = ( <" A B C D "> ++ <" E F G "> )

Proof

Step	Hyp	Ref	Expression
1		df-s3	|- <" E F G "> = ( <" E F "> ++ <" G "> )
2		s4cli	|- <" A B C D "> e. Word _V
3		s2cli	|- <" E F "> e. Word _V
4		df-s7	|- <" A B C D E F G "> = ( <" A B C D E F "> ++ <" G "> )
5		s4s2	|- <" A B C D E F "> = ( <" A B C D "> ++ <" E F "> )
6	1 2 3 4 5	cats1cat	|- <" A B C D E F G "> = ( <" A B C D "> ++ <" E F G "> )