Author Topic: Complex number question (Read 737 times) Tweet Share

rife168 · « **on:** June 28, 2012, 11:08:57 pm »

~~Sorry for using your thread TT, but I only have one question and didn't want to start a new thread.~~

Mod edit: As TT's thread is for his crazy uni maths, decided to split this post anyway

Would someone be able to point out the problem here?

$\sqrt{a}$
$=\sqrt{-1\times -1\times a}$
$=\sqrt{-1}\times \sqrt{-1}\times \sqrt{a}$
$=i\times i\times \sqrt{a}$
$=i^2 \sqrt{a}$
$=-\sqrt{a}$
$=$ wut.

pi · « **Reply #1 on:** June 28, 2012, 11:16:48 pm »

$\sqrt{mn} = (\sqrt{m})(\sqrt{n})$ ONLY if $m$ and $n$ are positive numbers

Hence, your third line is incorrect, and remember that the definition of an imaginary number is $i^2 = -1$ and not $i = \sqrt{-1}$

That's the rule (pity they don't write that last part in textbooks).

rife168 · « **Reply #2 on:** June 28, 2012, 11:22:21 pm »

Quote from: VegemitePi on June 28, 2012, 11:16:48 pm

$\sqrt{mn} = (\sqrt{m})(\sqrt{n})$ ONLY if $m$ and $n$ are positive numbers

Hence, your third line is incorrect.

That's the rule (pity the don't write that last part in textbooks).

Thanks Vege, you learn something new everyday!

pi · « **Reply #3 on:** June 28, 2012, 11:23:46 pm »

No probs, I also edited my post to include an extra line of info too

Search the forums now!

We have moved!

Author Topic: Complex number question (Read 737 times) Tweet Share

rife168

Complex number question

pi

Re: Complex number question

rife168

Re: Complex number question

pi

Re: Complex number question

Recent Posts

User:
Password: