if cos a = 1/3 then the positive value of tan 1/2a is? i did radical 2/3 over 4/3, but im not sure what to do now.

1 answer:

6 0

Hello,

$tg( \frac{a}{2} )=\pm \sqrt{ \dfrac{1-cos(a)}{1+cos(a)} } \\
=\pm \sqrt{ \dfrac{ \dfrac{2}{3} }{ \dfrac{4}{3} } } =\pm \sqrt{ \dfrac{1}{2} } =\pm \dfrac{ \sqrt{2} }{2} \\

+\ if\ \dfrac{a}{2}\ in\ 1\ quadrant\ (or \ 3)}\\

-\ if\ \dfrac{a}{2}\ in\ 2\ quadrant\ (or \ 4)}\\
$

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