Results 1 to 2 of 2

Math Help - Pf there is no wff of length 2

  1. #1
    Newbie
    Joined
    Apr 2009
    Posts
    1

    Pf there is no wff of length 2

    How does one show that there are no wff's of length 2,3 or 6, but that any other positive length is possible? It seems obvious I just don't know how to express it as a proof.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member
    Joined
    Nov 2008
    Posts
    394
    Quote Originally Posted by krystalballz View Post
    How does one show that there are no wff's of length 2,3 or 6, but that any other positive length is possible? It seems obvious I just don't know how to express it as a proof.

    Let L(S) be a length of an expression S.

    Each sentence symbol x is a well-formed formula of L(x)=1.

    For example,

    For a wff a, L(( \neg a)) = L(a) + 3.
    For wff a,b, L((a \wedge b)) = L(a) + L(b) +3.

    Now, we have wff's of length 1, 4, and 5. You can check the remaining cases inductively and make sure that no wff's of length 2,3 or 6 is possible.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. [SOLVED] Arc Length and Chord Length
    Posted in the Trigonometry Forum
    Replies: 7
    Last Post: December 22nd 2010, 01:24 AM
  2. Length needed from a known length and angle
    Posted in the Geometry Forum
    Replies: 4
    Last Post: July 21st 2009, 06:17 AM
  3. arc length and parameterized curve length
    Posted in the Calculus Forum
    Replies: 1
    Last Post: December 5th 2008, 02:33 AM
  4. Arc length and chord length
    Posted in the Geometry Forum
    Replies: 8
    Last Post: December 19th 2007, 03:20 PM
  5. Another arc length
    Posted in the Calculus Forum
    Replies: 3
    Last Post: October 25th 2007, 02:14 PM

Search Tags


/mathhelpforum @mathhelpforum