# formula

• June 11th 2009, 05:02 AM
the undertaker
formula
r = a*sqrt(b^2-c^2)

What does b equal to?
• June 11th 2009, 05:08 AM
Amer
Quote:

Originally Posted by the undertaker
r = a*sqrt(b^2-c^2)

What does b equal to?

$r=a(\sqrt{b^2-c^2})$

$r^2=a^2(b^2-c^2)$

$\frac{r^2}{a^2} = b^2 - c^2$

$\frac{r^2}{a^2} + c^2 = b^2$

$b=\sqrt{ \frac{r^2}{a^2} - c^2}$

that what you mean
• June 11th 2009, 05:21 AM
flyingsquirrel
Quote:

Originally Posted by Amer
$\frac{r^2}{a^2} + c^2 = b^2$

$b=\sqrt{ \frac{r^2}{a^2} - c^2}$

No, the last line should read $\sqrt{b^2}=\sqrt{ \frac{r^2}{a^2} + c^2}$ and as $\sqrt{b^2}=|b|$, there are two solutions : $\pm\sqrt{ \frac{r^2}{a^2} + c^2}$.