Вычислите: \(\frac{\cos540^{\circ}-\sin810^{\circ}}{\ctg\frac{5\pi}{2}-\tg(-\frac{9\pi}{4})}.\)

• \(1\)
• \(-2\)
• \(\frac{\sqrt{2}}{2}\)
• \(-\frac{\sqrt{3}}{2}\)