Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Am I correct or is Wolfram correct?

  1. Jan 25, 2013 #1
    4/5t + 7 = 47

    I say

    4/5t = 40

    t = 50

    but wolfram says t = 1/50

    Sorry I have to learn how to use latex again -_-
     
  2. jcsd
  3. Jan 25, 2013 #2

    berkeman

    User Avatar

    Staff: Mentor

    You need to add quotes to make it what you want: (4/5)t + 7 = 47

    Wolfram thinks you want it to be (4/5t) + 7 = 47
     
  4. Jan 25, 2013 #3

    jbriggs444

    User Avatar
    Science Advisor

    I think the delta is whether 4/5t = 40 is interpreted as 4/(5t) = 40 or (4/5)t = 40

    The standard convention is that multiplication and division bind equally tightly even when multiplication is indicated by juxtaposition and that both are left-associative. That means the latter interpretation is conventional. Barring some typography that OP has not copied carefully, OP is correct and Wolfram is in error.
     
  5. Jan 25, 2013 #4

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Add parentheses (), not quotes " ".
     
  6. Jan 28, 2013 #5
  7. Jan 28, 2013 #6

    pwsnafu

    User Avatar
    Science Advisor

    Mathematica is sensitive to spaces. It doesn't have much choice as it needs to be able to distinguish between "xy" and "x y" (the former is a variable with name xy while the latter is the product of two variables x and y).

    Same thing here: if you type "4/5 t" (with the space) it'll be parsed as ##\frac{4t}{5}##.
     
  8. Jan 28, 2013 #7
    The obvious part of this discussion as it relates to OP, make sure to look at the input interpretation when you enter formulas. Wolfram clearly displays how it interprets your input, if it does not match your equation then the answer will not match either. logic 101
     
  9. Jan 28, 2013 #8

    rollingstein

    User Avatar
    Gold Member

    Yes, but only when multiplication is explicitly indicated.

    e.g.Even wolfram uses the convention if told 4/5*t

    For implied multiplications I'm with Wolfram. Implied multiplications ought to bind tightest as a convention; that makes intuitive sense to me.
     
  10. Jan 28, 2013 #9

    jbriggs444

    User Avatar
    Science Advisor

    Ahh, sensible. That case did not come up when learning parsing rules in comp sci -- we never used juxtaposition to denote multiplication.
     
  11. Jan 28, 2013 #10

    rollingstein

    User Avatar
    Gold Member

    Right. Most modern programming languages would throw an error for doing an implied multiplication.

    Come to think of it, which other languages allow something like 5t instead of 5*t?
     
  12. Jan 28, 2013 #11
    [QUOTstein;4246799]Right. Most modern programming languages would throw an error for doing an implied multiplication.

    Come to think of it, which other languages allow something like 5t instead of 5*t?[/QUOTE]

    As far as languages go, I don't think any would interpret 5t ad 5*t .

    Wolfram does do implied multiplication and will interpret 5t as the product of the 2. The problem here is the 5t being in the denominator.

    If we expected wolfram to interpret 4/5t as (4/5)*t , then we would have to make a concession for the case of 4/(5t) by use of brackets.

    In either case, 4/5t is ambiguous when written line style so brackets are required for clarification.
     
  13. Jan 28, 2013 #12
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Am I correct or is Wolfram correct?
  1. Is this correct? (Replies: 3)

  2. Correct me if I am wrong (Replies: 14)

Loading...