p215 q10

thanks

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- Mar 25th 2008, 08:38 AMafeasfaerw23231233trigo problem no. 24 [general solution]
p215 q10

thanks - Mar 25th 2008, 09:50 PMafeasfaerw23231233
i didn't treat cos 2x as cos ^2 x

- Mar 26th 2008, 02:51 AMmr fantastic
1. Your answer of $\displaystyle \frac{2n\pi}{3} \pm \frac{\pi}{6}$ is correct, the book's answer of $\displaystyle 2n\pi + \frac{\pi}{6}$ misses solutions $\displaystyle \left( \text{such as} \, \frac{5\pi}{6} \, \text{and} \, \frac{\pi}{2}\right) $ and so is not completely correct .....

2. $\displaystyle \cos^{-1} \left( \frac{-1 + \sqrt{5}}{4} \right) = \frac{2 \pi}{5}$ and $\displaystyle \cos^{-1} \left( \frac{-1 - \sqrt{5}}{4} \right) = \frac{4 \pi}{5}$ are correct exact values. Your corresponding answers are only decimal approximations to these exact answers. But it's a bit tough to expect someone to know these exact values!!!!

It's possible to prove that these are the exact values but it's a bit complicated. - Mar 26th 2008, 03:53 AMtopsquark