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Compute the limit of the given function

Evaluate the limit.

    \[ \lim_{x \to 1} (2-x)^{\tan \left( \frac{\pi x}{2} \right) }. \]


First, we use the continuity and definition of the exponential,

    \begin{align*}  \lim_{x \to 1} (2-x)^{\tan \left( \frac{\pi x}{2} \right)} &= \lim_{x \to 1} e^{ \tan \left( \frac{\pi x}{2} \right) \cdot \log (2-x) } \\[9pt]  &= \exp \left( \lim_{x \to 1} \tan \left( \frac{\pi x}{2} \right) \log (2-x) \right). \end{align*}

Next, we use that \tan \frac{\pi x}{2} = \frac{1}{\cot \frac{\pi x}{2}} to rewrite the term in the limit in the indeterminate form 0/0 and apply L’Hopital’s rule,

    \begin{align*}  \exp \left( \lim_{x \to 1} \tan \left( \frac{\pi x}{2} \right) \log (2-x) \right) &= \exp \left( \lim_{x \to 1} \frac{\log (2-x)}{\cot \frac{\pi x}{2} } \right) \\[9pt]  &= \exp \left( \lim_{x \to 1} \frac{-\frac{1}{2-x}}{-\frac{\pi}{2} \frac{1}{\sin^2 \frac{\pi x}{2}}} \right) \\[9pt]  &= \exp \left( \lim_{x \to 1} \frac{2 \sin^2 \left( \frac{\pi x}{2} \right)}{\pi(2-x)} \right) \\[9pt]  &= e^{\frac{2}{\pi}}. \end{align*}

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