Solving roots- Without rooting?

[AGThePoet]

Hi, im trying to solve a way to do an eqaution via PHP, and due to certain restrictions on it i cant just square/cube/whatever root it. Well, i can square root, but i need to do it with any level of root. The equation i need to know how to solve is:

 

PS not sure how the forum formats, this maybe wont turn out.

-----______________

--T/-----------E

---/--------------------

/--------------P

 

EDIT: sorry that looks horrible, i had to add the dashes or else it collpases the whole thing tot he side..

 

if it doesnt work., ill edit it and fix it after i post it.

 

 

So it the T root of (e divided by p)... anyways, here are the rules i need the solutions to follow:

 

No actual square/cube/whatever roots

Only multiplying, dividing, adding, subtracting

Exponents can be used, but only if its a single term or multiple terms multiplied together... meaning no (E + P) squared. No adding/subracting inside the exponent range. foiling would be extrememly difficult to follow with generic programming when T could be anything.,

 

Thanks for any and all help

 

Alex

[Wannabe Genius]

ok this is a reasonably easy one.

 

$t = 'T'; // Insert value for T

$x = E/P;

$y = pow($t, $x);

echo $y;

 

By raising T to the power of a fraction less than 1, you are therefore working out the square root.

 

I havent actually tried this example, but have written similar ones in both PHP and Python. You've probably seen it done before. In M$ Excel.

 

Whilst this does not follow most of your rules, the value of T is irrelevent as long as E/P always evaluates correctly. It is, however, generic to the point of accepting any root where a fraction can be determined.

[AGThePoet]

$E = $_POST['E'];
$P = $_POST['P'];
$T = $_POST['T'];
$X= ($E/$P);
$Y = pow($T, $X);
print $Y; 

 

just to put it in correct PHP syntax

 

Ill go test it now

[Wannabe Genius]

hmm I've got a funny feeling I've missed a step out. checking now

[AGThePoet]

lol, okay, ill let you know what happens with the current code once ive finished testing

[Wannabe Genius]

Ok, IF I'm right I've written this out backwards. I've written it as T^E/P and it SHOULD be E/P^1/T -- apologies. it IS 2:40am here in sunny England and its beena long day.

[AGThePoet]

lol, i fixed it, is this how you did it?

 

<?php

$AT = $_POST['T'];

$E = $_POST['E'];

$P = $_POST['P'];

$T = $_POST['T'];

$T = (1/$T);

$X = ($E/$P);

$Y = pow($X, $T);

$Y--;

$Y = ($Y*100);

print "You inputted the following:";

echo "

";

print "Principle: $ $P";

echo "

";

print "Time: $AT days";

echo "

";

print "End Result: $ $E";

echo "

";

echo "

";

print "Interest: $Y %";

echo "

";

?>

 

 

ANyways, thanks for the help, i havent been able to get it to work until now

[AGThePoet]

oh, btw, the result is here: http://members.lycos.co.uk/agthepoet/test/index3.html not sure how long i will keep it in that location but you can check it out quick

[Wannabe Genius]

pretty much. I've been using this for some pretty nasty fractions and it hasn't let me down (yet). That pow() function can be hellishly useful.

 

Sometimes even M$ has its uses. If only to learn functions for porting elsewhere.

 

I checked out your results page and it did seem to be working ok although I did get a bit confused as to what values I was inputting, but for a simple test it looked fine.

[AGThePoet]

yeah, its not "cosmetically" set yet, just PHP functional. ill make it look better later

 

basically, its a loan program, where you enter 3 things:

 

Principal- Amoutn of money you put it

Time- amount of time in days the money coolects interest

Ending- Amount of money it has at the end.

 

THen it finds the interest % needed daily to get those results

[Wannabe Genius]

I kinda figured that out after I saw the result. The main think is though, it works.

[AGThePoet]

yep