If \(\cos x\) and \(\sin x\) are solutions of the differential equation \(a_{0} \frac{d^{2} y}{d x^{2}}+a_{1} \frac{d y}{d x}+a_{2} y=0\) where \(a_{0}, a_{1}\) and \(a_{2}\) are real constants, then which of the following is/are always true?

1. A \(A \cos x+B \sin x\) is a solution, where \(A\) and \(B\) are feal constants
2. B \(A \cos \left(x+\frac{\pi}{4}\right)\) is a solution, where \(A\) is a real constant
3. C \(A \cos x \sin x\) is a solution, where \(A\) is a real constant
4. D \(A \cos \left(x+\frac{\pi}{4}\right)+B \sin \left(x -\frac{\pi}{4}\right)\) is a solution, where A and \(B\) are real constants