MCQ
If $\tan20^\circ+\tan40^\circ+\sqrt{3}\tan20\circ\tan40^\circ$ is equal to:
  • A
    $\frac{\sqrt{3}}{4}$
  • B
    $\frac{\sqrt{3}}{2}$
  • $\sqrt{3}$
  • D
    $1$

Answer

Correct option: C.
$\sqrt{3}$
$\tan20^\circ+\tan40^\circ+\sqrt{3}\tan20^\circ\tan40^\circ$
$=\tan60^\circ(1-\tan20^\circ\tan40^\circ)+\tan60^\circ\tan20^\circ\tan40^\circ$
$=\tan60^\circ-\tan60^\circ\tan20^\circ\tan40^\circ+\tan60^\circ\tan20^\circ\tan40^\circ$
$=\tan60^\circ$
$=\sqrt{3}$

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