Question 1038664
<font face="Times New Roman" size="+2">


One question per post, please.


For the first one you need to do a conditional proof.  Note that by DeMorgan, your conclusion is equivalent to ~C or ~B.


First assume B, then, having been given A, you have B and A, and then you have D by Modus Ponens.  But D is the same as ~~D.  ~~D makes ~C out of statement 3 by Modus Tollens.  And ~C gives you ~C or ~B.


Second assume ~B which gives you ~C or ~B directly.


So either way, you get the desired conclusion.


John
*[tex \LARGE e^{i\pi}\ +\ 1\ =\ 0]
My calculator said it, I believe it, that settles it
<img src="http://c0rk.blogs.com/gr0undzer0/darwin-fish.jpg">
*[tex \Large \ \
*[tex \LARGE \ \ \ \ \ \ \ \ \ \  

</font>