# help with solving a half angle identity

• October 21st 2010, 09:16 PM
wonderd
help with solving a half angle identity
Im not exactly sure how the square root of 1-(-1/3)/2 = the square root of 2/3?

Can someone explain this for me?
• October 21st 2010, 09:25 PM
Prove It
$\displaystyle \sqrt{\frac{1 - \left(-\frac{1}{3}\right)}{2}} = \sqrt{\frac{1 + \frac{1}{3}}{2}}$

$\displaystyle = \sqrt{\frac{\frac{4}{3}}{2}}$

$\displaystyle = \sqrt{\frac{4}{6}}$

$\displaystyle = \sqrt{\frac{2}{3}}$.

P.S. Please use brackets where they're needed, what you posted looks lke $\displaystyle 1 - \frac{\left(-\frac{1}{3}\right)}{2}$...
• October 21st 2010, 09:33 PM
wonderd
so you go from \sqrt{\frac{\frac{4}{3}}{2}} to \displaystyle = \sqrt{\frac{2}{3}} by multiplying the 2 by the 3 and leaving the 4 ontop?
• October 21st 2010, 09:43 PM
wonderd
i think i understand, you dont know how much i appreshiate the help ! :)