formula

**the undertaker** · June 11th 2009, 05:02 AM

r = a*sqrt(b^2-c^2)

What does b equal to?

**Amer** · June 11th 2009, 05:08 AM

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

**flyingsquirrel** · June 11th 2009, 05:21 AM

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 : $\pm\sqrt{ \frac{r^2}{a^2} + c^2}$ .

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