- $\frac{{\cos x - \sin x}}{{{e^2}^x}}$
- $\frac{{\cos x.{e^x} + \sin x.{e^x}}}{{{e^2}^x}}$
- $\frac{{\cos x - \sin x}}{{{e^x}}}$
- $\frac{{\cos x + \sin x}}{{{e^2}^x}}$