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If cos X = $\dfrac{2}{3}$ then tan X is equal to:

$\dfrac{5}{2}$
$ \sqrt{\dfrac{2}{3}}$
$\dfrac{\sqrt{5}}{2}$
$\dfrac{2}{\sqrt{5}}$
Explanation:

By trigonometry identities, we know:

$1 + tan^{2}X $= $sec^{2}X$

And sec X = $\dfrac{1}{cos X}$ =$ \dfrac{1}{(\dfrac{2}{3})}$ =$ \dfrac{3}{2}$

Hence,

$1 + tan^{2}X$ = $(\dfrac{3}{2})^{2}$ =$ \dfrac{9}{4}$

$tan^{2}X$ = $(\dfrac{9}{4}) $– 1 = $\dfrac{5}{4}$

tan X = $\dfrac{\sqrt{5}}{2}$

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