Help me please to find a solution for the last formula in exercise 12.8. from "Introduction to mathematical logic" by A.Church. Here it is:
Prove as theorem of without making use of the fourth axiom :
.
Help me please to find a solution for the last formula in exercise 12.8. from "Introduction to mathematical logic" by A.Church. Here it is:
Prove as theorem of without making use of the fourth axiom :
.