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Last updated date: 07th Dec 2023
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# Find the value of $2{{\tan }^{-1}}\left( \dfrac{1}{2} \right)$.A. ${{\cos }^{-1}}\left( \dfrac{3}{5} \right)$ B. ${{\cos }^{-1}}\left( \dfrac{3}{4} \right)$ C. ${{\cos }^{-1}}\left( \dfrac{5}{3} \right)$ D. ${{\cos }^{-1}}\left( \dfrac{1}{2} \right)$

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Hint: For solving this question you should know about finding the values of inverse trigonometric functions. In this problem we can find the inverse trigonometric values of the given functions by using the formulas. But if it is given to find the value of a trigonometric function, then we find the trigonometric value of that function and then we add them according to the given sequence.

According to our question it is asked of us to find the correct option for the value of $2{{\tan }^{-1}}\left( \dfrac{1}{2} \right)$. As we know that if any question is asking for the values of trigonometric functions, then we directly put the value of that function there and get our required answer for that. But if it is given to find the angles of them, then we find the original function (trigonometric function) for that value and then we get the angle of that by comparing it with each other. And if it is asked directly without any angle, then we always use the general formulas of trigonometry for solving this. And we will solve that according to the given sequence of calculations.
$f\left( x \right)=2{{\tan }^{-1}}\left( \dfrac{1}{2} \right)$
As we know that $\left\{ \because 2{{\tan }^{-1}}x=\tan \left( \dfrac{2x}{1-{{x}^{2}}} \right) \right\}$
\begin{align} & ={{\tan }^{-1}}\left( \dfrac{2\times \dfrac{1}{2}}{1-{{\left( \dfrac{1}{2} \right)}^{2}}} \right) \\ & ={{\tan }^{-1}}\left( \dfrac{1}{1-\dfrac{1}{4}} \right) \\ & ={{\tan }^{-1}}\left( \dfrac{4}{3} \right) \\ & ={{\cos }^{-1}}\left( \dfrac{3}{5} \right) \\ \end{align}