KazLovedsbd
KazLovedsbd KazLovedsbd
  • 21-09-2016
  • Mathematics
contestada

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.

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caylus
caylus caylus
  • 21-09-2016
Hello,

[tex]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)}\\ [/tex]
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