Hatrack River Forum: Insufficient realness, does not commute

This is topic Insufficient realness, does not commute in forum Books, Films, Food and Culture at Hatrack River Forum.

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Posted by King of Men (Member # 6684) on :

Note to self: Taking the real part and multiplying only commute when dealing with negligible imaginary parts. Doing so for large imaginary parts is a bug! A three-day bug, in fact.

Posted by MightyCow (Member # 9253) on :

Preach on, brother!

(anyone have a clue what's going on? I think KoM lost it)

Posted by HollowEarth (Member # 2586) on :

KoM means that: Re[a+b*i]*Re[x+y*i] = Re[(a+b*i)*(x+y*i)] only if the imaginary parts (b and y) are very small.

Speaking of errors, I was bitten by the "Hz^2 per Hz, but don't cancel the Hz" unit insanity today. Doh. My favorite part is when you have to magic that one Hz back out, since your normal unit analysis can't actually see it.

Posted by Shigosei (Member # 3831) on :

Um...the real part and multiplying work from home?

My guess is that KOM is working with complex numbers and was doing some sort of operation where the order of the terms matters if there's a large imaginary part involved.

Posted by Nighthawk (Member # 4176) on :

"Sorry, chap, but I don't get that banter at all."

Posted by BlackBlade (Member # 8376) on :

quote:
KoM means that: Re[a+b*i]*Re[x+y*i] = Re[(a+b*i)*(x+y*i)] only if the imaginary parts (b and y) are very small.

But of course! It's embarrassing that I didn't understand that at first glance. [Wink]