# Infinity*0 = -1 ?

ExecNight

## Main Question or Discussion Point

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?

matt grime
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?

ExecNight
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.

LeonhardEuler
Gold Member
Yeah and:
tan(0)*tan(-90)=-1
→ 0*-$\infty$=-1
→ 0*$\infty$=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:
arildno
Homework Helper
Gold Member
Dearly Missed
ExecNight said:
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.
:rofl:
This is just so silly..
BTW, the tangens function is not defined at 90 degrees, so you can't evaluate it there.

ExecNight
Oh well, i need to rewrite all the history behind an equation while asking a question?

arildno
Homework Helper
Gold Member
Dearly Missed
ExecNight said:
Oh well, i need to rewrite all the history behind an equation while asking a question?
You must tell us what YOU mean by the terms you happen to use.

ExecNight said:
Oh well, i need to rewrite all the history behind an equation while asking a question?
Yes, since you happen not to know it!

ExecNight
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

arildno
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:
Zurtex
Homework Helper
ExecNight said:
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.
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.

Hurkyl
Staff Emeritus
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?

LeonhardEuler
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.

Hurkyl
Staff Emeritus