Gah, trig again!

[droodles]

shut up u liar

[Mao]

(as only the negative sqrt is applicable in this case)

but why?

either i've misread somewhere, or there's an implied domain i missed:

solving in positive sqrt:










which is the same as your approximate....

wth is going on?! (its too late for me to think atm)


regardless, ur now known to me as Ahmad-II xD

[Odette]

anyone could do that with the right toolbox

You are too modest dcc, just accept it, you're intelligent

[dcc]

well it does too mao, i wonder why i wrote that :|

[Mao]

well it does too mao, i wonder why i wrote that :|

i'm more concerned with...
why do they work out to be the same!!!! =S

but still, you actually did it =P

PS: we do take tangents in math boards.

PPS: dcc, did u go on wikipedia? =P

[dcc]

Its a trick I picked up a while ago solving a quartic in Ahmad's recreational thread.  The substitution works on a type of cubic called a 'depressed' cubic, so it was lucky you gave one as that, otherwise there would he hell to substitute.

[Mao]

in that case:
http://en.wikipedia.org/wiki/Cubic_function#Cardano.27s_method

now you can solve all of it =)