Thursday, February 5, 2015

Hi, need some help on the following question!! find the possible values of tan(1/2)x, if tanx=3/4 thanks A Ui need the method explained as clearly...

`tan(x)= 3/4`


``We need to
find the value of `tan(1/2)x = tan(x/2)`


`We know
that:`


`tan(x)=
sin(x)/cos(x)`


`==> sin(x)/cos(x)=
3/4`


`==> 3cos(x)=
4sin(x)`


Now we know that `sin^2 x+ cos^2 x = 1 ==>
cosx = sqrt(1-sin^2 x)`


`==> 3sqrt(1-sin^2 x)=
4sin(x)`


``Now we will square both
sides:


`==> 9(1-sin^2 x) = 14sin^2
x`


`==> 9 - 9sin^2 x == 14sin^2
x`


`==> 25sin^2 x =
9`


`==> sin^2 x =
9/25`


`==> sin(x)=
3/5`


`==> cos(x)=
4/5` ..................(2)


Now we know
that:


`cos(2x)= 1- 2sin^2
x`


`==> cos(x)= 1- 2sin^2
(x/2)`


`==> 4/5 = 1- 2sin^2
(x/2)`


`==> 2sin^2 (x/2) = 1-
4/5`


`==> 2sin^2 (x/2)=
1/5`


`==> sin^2 (x/2)=
1/10`


`==> sin(x/2)=
1/sqrt10`


``Now we know
that:


`sin^2 (x/2) + cos^2 (x/2)=
1`


`==> cos(x/2)= sqrt(1-sin^2
(x/2))`


`==> cos(x/2)= sqrt(1-
1/10)`


`==> cos(x/2)= sqrt(9/10) =
3/sqrt10`


`==> tan(x/2)= sin(x/2) /
cos(x/2)`


`==> tan(x/2)= (1/sqrt10) / (3/sqrt10) =
1/3`


`==> tan(x/2)=
1/3`


``

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