Proof formats, homework 4

Intensional Logic Proof Formats, Homework 4:

Exercises (due 8 March):
- 4.34, 4.35, 4.36 (a), 4.37 (b).
  
  You may appeal to theorems from the chapter, notably 4.2, 4.3, 4.4, 4.5, 4.10. If you use such theorems, you must cite them when you do.
  
  The format of your proofs should be as follows:
  - When showing that A_n is a theorem of Sigma:
    
    1. |-_Sigma A₁ justification
    
    2. |-_Sigma A₂ justification
    
    .
    
    .
    
    .
    
    n. |-_Sigma A_n justification
  - When showing that A₁ therefore A_n is a rule of inference under which Sigma is closed:
    
    1. |-_Sigma A₁ "Supposition" (note that, unlike the book, I include the single turnstile!)
    
    2. |-_Sigma A₂ justification
    
    .
    
    .
    
    .
    
    n. |-_Sigma A_n justification

Justifications should consist of citing either a theorem known to be in sigma or an inference rule under which sigma is known to be closed. Technically, these aren't proofs within a formal axiomatic proof-system, but will still nonetheless look very much like such proofs.

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Last modified: "Sunday, 01 Jan 06, 13:57"

1.	\|-_Sigma	A₁	justification
2.	\|-_Sigma	A₂	justification
.
.
.
n.	\|-_Sigma	A_n	justification

1.	\|-_Sigma	A₁	"Supposition" (note that, unlike the book, I include the single turnstile!)
2.	\|-_Sigma	A₂	justification
.
.
.
n.	\|-_Sigma	A_n	justification