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Question

Question: If \(\cosh\alpha = \sec x,\) then \(\tan^{2}\frac{x}{2} =\)...

If coshα=secx,\cosh\alpha = \sec x, then tan2x2=\tan^{2}\frac{x}{2} =

A

cos2α2\cos^{2}\frac{\alpha}{2}

B

sin2α2\sin^{2}\frac{\alpha}{2}

C

cot2α2\cot^{2}\frac{\alpha}{2}

D

tanh2α2\tan h^{2}\frac{\alpha}{2}

Answer

tanh2α2\tan h^{2}\frac{\alpha}{2}

Explanation

Solution

coshα=secx=1cosx=11tan2x21+tan2x2{\cos h}\alpha = \sec x = \frac{1}{\cos x} = \frac{1}{\frac{1 - \tan^{2}\frac{x}{2}}{1 + \tan^{2}\frac{x}{2}}}

coshα1=1+tan2x21tan2x2\frac{\cos h\alpha}{1} = \frac{1 + \tan^{2}\frac{x}{2}}{1 - \tan^{2}\frac{x}{2}} \Rightarrow coshα1coshα+1=2tan2x22=tan2x2\frac{{\cos h}\alpha - 1}{{\cos h}\alpha + 1} = \frac{2\tan^{2}\frac{x}{2}}{2} = \tan^{2}\frac{x}{2}

\Rightarrow 2sinh2α22cosh2α2=tan2x2\frac{2\sin h^{2}\frac{\alpha}{2}}{2\cos h^{2}\frac{\alpha}{2}} = \tan^{2}\frac{x}{2} \Rightarrow tanh2α2=tan2x2{\tan h}^{2}\frac{\alpha}{2} = \tan^{2}\frac{x}{2}