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find the exact value of sin(t/2) if tan(t)=12/5 and pie

 Jul 13, 2016
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\(\tan t=\frac{12}{5}\\ hypotenuse = \sqrt{5^2+12^2}=13\\ \cos \space t= \frac{5}{13} \\\quad\sin(\frac{t}{2})\\= \pm\sqrt{\frac{1-\cos t}{2}}\\=\pm\sqrt{\frac{1-\frac{5}{13}}{2}}\\=\pm\sqrt{\frac{\frac{8}{2}}{13}}\\\)

\(=\pm\sqrt{\frac{4}{13}}\\=\frac{\pm2}{\sqrt{13}}\)

\(\because \space \tan t \space is \space positive\\\therefore \sin(\frac{t}{2})\space is\space positive\space too\)

\(\therefore \sin(\frac{t}{2})=\frac{2\sqrt{13}}{13}\space OR \frac{2}{\sqrt{13}}\)

By the way, why pie?

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 Jul 14, 2016
edited by MaxWong  Jul 14, 2016

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