We need to differentiate the function \( f(x) = \sin x e^{\sin x} \). To do this, we will use the product rule for differentiation:
\[
\frac{d}{dx} [u \cdot v] = u' \cdot v + u \cdot v'
\]
Here, let \( u = \sin x \) and \( v = e^{\sin x} \). Then:
- \( u' = \cos x \),
- \( v' = e^{\sin x} \cdot \cos x \) (using the chain rule).
Now applying the product rule:
\[
f'(x) = \cos x \cdot e^{\sin x} + \sin x \cdot e^{\sin x}
\]
Thus, the derivative of \( f(x) \) is \( f'(x) = \cos x e^{\sin x} + \sin x e^{\sin x} \), so the correct answer is (A).