If \(f(x) = \sin x e^{\sin x}\), find \(f'(x)\)
If \(tan(x - y) = \frac{4}{5}\), \(\tan(x + y) = \frac{6}{5}\), then \(\tan(2x) =\)
If \(f(x)\) is continuous in \(\mathbb{R}\),
find \(k\).