# can x^2 + y^2 = square root of -4?

Discussion in 'Computer Support' started by Solar^, Jan 28, 2006.

1. ### Solar^Guest

I'm not sure if this is the forum for this but here goes:
In pre-calc were doing equations of circles, anyway have come up with
the equation for a circle that involves taking the square root of a
negative number to determine the radius. Don't know how to handle
this, thought some of you computer science/math guys might know.
Regards,
Solar^

Solar^, Jan 28, 2006

2. ### GordonGuest

isn't the square root of a negative number irrational or complex? (Been
a *very* long time since I did this - about 30 years!)

Gordon, Jan 28, 2006

3. ### Geoff PearsonGuest

yes squ rt of -4 is 2i where i= sq rt of -1 (whatever that is!)

Geoff Pearson, Jan 28, 2006
4. ### Solar^Guest

Gordon,
Thanks for the reply. The resulting number would be imaginary or " i "
and I'm wondering if the radius of a circle can even be imaginary?
Regards,
Solar^

Solar^, Jan 28, 2006
5. ### BudweiserGuest

Take a look here
http://www.mat.bham.ac.uk/maths_extension/book_files/complex.pdf

section 9 is probably what you are looking for,the rest you should be
able to class as revision.
Do not forget--all you are doing is resolving a triangle--albeit
constrained,be carefull to asses your calc to ensure you have the result
some other stuff

remember a circle can also be enclosed by a square,thus the radius can
be determined.

Budweiser, Jan 28, 2006
6. ### philoGuest

imaginary numbers are often needed for calulating ...
\i recall a lot of it from when i was in engineering school...
some time in the previous century!

philo, Jan 28, 2006
7. ### Mike EasterGuest

Is this a radius of an imaginary circle? As in one with a negative
area?
I like wikipedia's discussion of imaginary numbers, especially because
they point out that all numbers are abstract anyway, including zero and
negative and fractional numbers in some contexts. Thus the abstract
imaginary numbers which represent i as the square root of -1 in the
complex number equation a + bi are as real and useful for their
functionality as are all of the rest of the number abstractions.

http://en.wikipedia.org/wiki/Imaginary_number Imaginary number
Numbers" Really Exist?

Mike Easter, Jan 28, 2006

[flashback] My last term in engeneering was Spring 1966 at Michigan State.
Holy shit -- that's been 40 years now. They've probably discovered new
numbers that we didn't even know about back then. There's certainly lots
more for the physics and chem boys to know than there was back in those
days.

Blinky the Shark, Jan 28, 2006
9. ### GordonGuest

Wow! You old git!

Gordon, Jan 28, 2006
10. ### old jonGuest

That only makes you older than 6 philo <g>.

old jon, Jan 28, 2006
11. ### Solar^Guest

I simplified the equation in the header just to find out if a circle
could indeed have an imaginary radius. I guess from all of the replies
that it can, if it is given that it is an imaginary circle to begin
with: the entire equation is as follows in case someone is interested:
x^2 + y^2 - 6x + 4y + 13 = 0
(x-3)^2 + (y+2)^2 = -2
so the center is C(3,-2) radius = square root of -2 or 2i
Thanks again guys, I'll see what the prof says on Monday.

Solar^, Jan 28, 2006

You betcha!

Wrote my first program in 1965. Fortran. Punch cards.

Blinky the Shark, Jan 28, 2006
13. ### clotGuest

Wow! This takes me back! And: ALGOL, punch tape.....

clot, Jan 28, 2006

And the business majors were doing COBOL.

Blinky the Shark, Jan 28, 2006
15. ### clotGuest

Yup and I never got to learn that one!

clot, Jan 28, 2006
16. ### philoGuest

Yep...
i wrote my first Fortran program in 1968...
hated those punch cards so much i stayed away from
computers for a good ten years...
but after i got my job...went back to night school
and took a few more courses...
although they did have terminals then...
i was still using those damn punch cards as late as 1979 or so!!!
stayed away from computers again for many more years!!!!

Those good old days were not so good!!!!

philo, Jan 28, 2006
17. ### philoGuest

yep...I'm 7 years old ...

but in truth i was born in the first half of the previous
century...
now that's old

i sure remember those coal-burning steam locomotives well!!!!

philo, Jan 28, 2006
18. ### clotGuest

Shit. I'm still shovelling coal into the laptop to get it going.

clot, Jan 28, 2006
19. ### Toolman TimGuest

In clot spewed forth:
I upgraded mine to a perpetual motion machine.

Toolman Tim, Jan 28, 2006
20. ### clotGuest

Does that need Belkin protection when you use it?

clot, Jan 28, 2006