PDA

View Full Version : Doubling Force

LFC
10-23-2002, 04:50 PM
alright i've tried deriving this and i just dont get it..

for a rate of discount d...with the original force d. whats the double force? i keep getting {2d -dsquared}/{1-d}squared.
cant get rid of the denominator.

as an example, for an interest i, the double force is
2i +i(squared).
drctypea
10-23-2002, 05:00 PM
its 2d - d(squared) when you double force of interest and have d
its 2i + i(squared) " "" ""
its 2 delta "" ""
LFC
10-23-2002, 05:03 PM
its 2d - d(squared) when you double force of interest and have d
its 2i + i(squared) " "" ""
its 2 delta "" ""

yea man but how do u derive that?? i hate memorizing stuff...esp if its sthing which seems soooo easy to derive! i just dont get it.
Gandalf
10-23-2002, 05:09 PM
I thought I would avoid this like the plague, because I know in practice I would convert d to i, i to delta, double delta, convert that to a new i, convert that to a new d. But then, I wouldn't be under exam time constraints. Then again, I hate d's.

Having seen the answer and thought about it, it is just 1 - (1-d)^2.

By tomorrow I will have forgotten again.
retaker
10-23-2002, 05:11 PM
(1 - d) ^-1 = e^delta

[(1 - d) ^-1]^2 = e^2delta

[(1 - d) ^2]^-1

[(1 -2d +d^2]^-1

[(1 -(2d -d^2)]^-1
retaker
10-23-2002, 05:13 PM
It's best not to memorize things.
drctypea
10-23-2002, 05:16 PM
something like that though is pretty trivial and imo i dont think the derivation is necessary especially being that it is not hard to derive...
bg23516
10-23-2002, 05:19 PM
Firmly agree. Memorize those things. They are so easy, meaningless, and patterned that there is no reason to waste time on the exam.
retaker
10-23-2002, 05:26 PM
the thing is, though, that you probably aren't going to see this on the exam, so why waste your memory when you can do such a "trivial", as you say, derivation so quickly if you need it.
BTW, I am sure he appreciates that comment.
drctypea
10-23-2002, 05:31 PM
are you going to whine about this now? come on give it a rest mate
retaker
10-23-2002, 05:36 PM
I don't think I'm the one who needs to give it a rest. You are insulting this guy for asking this question because I chose to respond to his question.

I am getting sick of being civil in respose to closed minded conformist a_sholish statements.
drctypea
10-23-2002, 05:40 PM
wow...retaker is angry...i find this quite comical and choose not to waste my time arguing over such frivolousness...im sure lfc can defend himself and sure he realizes the comments werent meant to be derogatory. learn how to spell...good day.
LFC
10-23-2002, 05:46 PM
now now boys...just relax..why is everyone getting so uptight?
i agree it is trivial...and i do think memorizing sthing like that is best..however, i just wanted to know how its derived..thats all. under exam conditions i would simply recall it..not sit there and derive it even though yes, it is easy, and short. so no offence at all taken from my part. retaker, thanks for the derivation buddy. i get it now.

so boys, have a joint (can i say that) and relax. :)
retaker
10-23-2002, 05:57 PM
Thanks, I will.
Dr T Non-Fan
10-23-2002, 06:12 PM
I agree with retaker: deriving saves what limited space there is in some of our heads.
It becomes very useful when you can start with memorizing one formula and derive three other formulas from it.
Lex
10-25-2002, 05:19 PM
Way easier to derive the answer to this question...

:horse: