2.12.20 Asymptotic analysis

Condition: Write an asymptotic formula for a given \( f(x) \) for \( x \rightarrow a \), and the answer must contain at least two terms of the asymptotic formula, not counting the remainder. \[ f(x)=\left(\frac{2^{x}+1}{2}\right)^{1 / \sin x}, \quad x \rightarrow 0 \]