Answer
$=\dfrac {1}{4}\tan 68$
Work Step by Step
$\dfrac {2\tan \alpha }{1-\tan ^{2}\alpha }=\tan 2\alpha \Rightarrow \dfrac {\tan 34}{2\left( 1-\tan ^{2}34\right) }=\dfrac {1}{4}\dfrac {2\tan 34}{1-\tan ^{2}34}=\dfrac {1}{4}\tan 68$
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