`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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