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

Infinity*0 = -1 ?

  1. Aug 7, 2005 #1
    infinity*0 = -1 ???

    From Analitic Geometry;

    Tan(x) = m

    m1*m2 = -1


    Tan(0) * Tan (90) = -1

    Therefore;

    0 * infinity = -1

    What is wrong here?
     
  2. jcsd
  3. Aug 7, 2005 #2

    matt grime

    User Avatar
    Science Advisor
    Homework Helper

    you mean apart from the fact it's rubbish?

    what are m1 and m2? who says that they must satisfy that relation for *all* m1 and m2? they need not and they do not, even if I seconf gues what you mean, in fact this exact nonquestion has been asked beofer in this forum at least twice in the last couple of months. Why?
     
  4. Aug 7, 2005 #3
    Matt,

    How are you a "Math Guru" if you have no idea what is "tan(x) = m"

    in Analitic Geometry?

    Let alone you don't even know the Formula (m1*m2=-1) in that regard.
     
  5. Aug 7, 2005 #4

    LeonhardEuler

    User Avatar
    Gold Member

    Yeah and:
    tan(0)*tan(-90)=-1
    → 0*-[itex]\infty[/itex]=-1
    → 0*[itex]\infty[/itex]=1
    The problem is assuming that tan(90) is infinity. It isn't. It's sin(90)/cos(90)=1/0 which doesn't have any meaning

    edit:Matt knows m1m2=-1 for perpendicular lines, it just wasn't clear to him what m1 and m2 were in your post since you didn't say.
     
    Last edited: Aug 7, 2005
  6. Aug 7, 2005 #5

    arildno

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    :rofl:
    This is just so silly..
    BTW, the tangens function is not defined at 90 degrees, so you can't evaluate it there.
     
  7. Aug 7, 2005 #6
    Oh well, i need to rewrite all the history behind an equation while asking a question?
     
  8. Aug 7, 2005 #7

    arildno

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    You must tell us what YOU mean by the terms you happen to use.
     
  9. Aug 7, 2005 #8
    Yes, since you happen not to know it!
     
  10. Aug 7, 2005 #9
    Ok make a list here to me;

    - How many different m= tan(x) are used in "Analitic Geometry", where m1*m2=-1 ?


    Or do you think you are so "genius" when you come up with an idea that "m" might be any given number? So my question is an assumption on something i invented, so i should explain it to you... LOL
     
  11. Aug 7, 2005 #10

    arildno

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    First of all, the geometry you're talking about is neither syphilitic or analitic, it is "analytic".
    You must define the (non-elementary) symbols you use, period. If you are unwilling to do so, kindly f**k off.
     
    Last edited: Aug 7, 2005
  12. Aug 7, 2005 #11

    Zurtex

    User Avatar
    Science Advisor
    Homework Helper

    Ahh yes, tan(x) = m immediately clarifies what m1 and m2 are......

    If you are stuck on something and need our help, could you please clearly explain what it is.
     
  13. Aug 7, 2005 #12

    Hurkyl

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    ExecNight: you have until your next post to tone down the attitude.

    Did you ever stop to think that maybe, just maybe, we know what we're doing?

    Did you ever stop to think that when someone asks you a question, it might not be because they want to hear the answer, but because they want you to hear the answer?

    Did you ever stop to think that "what is wrong" might be hidden by your own sloppiness, and that by going over all the steps in full detail, your mistake would be utterly obvious?
     
  14. Aug 7, 2005 #13

    LeonhardEuler

    User Avatar
    Gold Member

    Yes, in most cases when a person writes m=tan(x), he is probably most often talking about the slope of a line, and then when you see m1m2=-1 after that, it probably makes most people think of perpendicular lines, but its possible that they are talking about something else. If you read matt grime's post you see that he understood what you probably meant, but just didn't reject the possiblity that you meant something else, that's all.
     
  15. Aug 7, 2005 #14

    Hurkyl

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Attack deleted. Thread closed.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?