For the value of $\frac{2 \tan (x)}{1-\tan ^2(x)}$ to be positive, find values of $x$, such that $x…

For the value of $\frac{2 \tan (x)}{1-\tan ^2(x)}$ to be positive, find values of $x$, such that $x \in\left(0, \frac{\pi}{2}\right)$
  1. $\left(0, \frac{\pi}{3}\right)$
  2. $\left(0, \frac{\pi}{6}\right)$
  3. $\left(0, \frac{\pi}{4}\right)$
  4. $\left(0, \frac{\pi}{8}\right)$

Solution

Given, $ \begin{aligned} & \frac{2 \tan x}{1-\tan ^2 x}>0 \\ & \tan 2 x>0 \end{aligned} $ Since, $\quad 0 < 2 x < \frac{\pi}{2} \quad\left[\because \tan 2 x\right.$ is the in $\left.Q_1\right]$ $ \begin{array}{ll} \Rightarrow & 0 < x < \frac{\pi}{4} \\ \therefore & 0 < x < \frac{\pi}{4} \text { as } x \in\left(0, \frac{\pi}{2}\right) \end{array} $ Hence, option (3) is correct

Asked in: AP EAMCET 2020 (22 Sep Shift 2)

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