# Thread: help with inverse function

1. ## help with inverse function

here is the formula S=f(x)= 6(pi)r^2
i believe that the inverse is r=sqrt s / 6 pi . am I correct or have I blundered.

2. Depends on where you decide to put your brackets. As it is your expression is ambiguous.

3. r= (sqrt s)/ (6pi) thats what i think the answer is

4. nope

$\displaystyle S = 6 \pi r^2$

$\displaystyle \frac S {6 \pi} = r^2$

$\displaystyle \sqrt {\frac S {6 \pi}} = r$

5. thanks matt.

I've got another question for the same problem f(r)=6*pi*r^2. this is what im trying to find. f^-1(f(r)).

heres what i know from the problem already.

f(r)= 6*pi*r^2
f(f^-1(s))= s

I was able to work that far but I cant mentally picture what the formula f^-1(f(r)) is. all I know is that the formulas should equal r.

6. Please post separate problems in a different thread. You might at this stage want to read the forum rules:

http://www.mathhelpforum.com/math-he...php?do=cfrules