Find the exact value of the expression. \( \cos 5^{\circ} \cos 25^{\circ}-\sin 5^{\circ} \sin 25^{\circ} \) \( \cos 5^{\circ} \cos 25^{\circ}-\sin 5^{\circ} \sin 25^{\circ}= \) (Simplify your answer, including any radicals. Use integers or fractions for any numbers in the expression.

To simplify the expression \(\cos 5^{\circ} \cos 25^{\circ} - \sin 5^{\circ} \sin 25^{\circ}\), we can use the cosine of the sum formula: \[ \cos(A + B) = \cos A \cos B - \sin A \sin B \] In our case, let \(A = 5^{\circ}\) and \(B = 25^{\circ}\). Then: \[ \cos 5^{\circ} \cos 25^{\circ} - \sin 5^{\circ} \sin 25^{\circ} = \cos(5^{\circ} + 25^{\circ}) = \cos(30^{\circ}) \] The cosine of \(30^{\circ}\) is well-known: \[ \cos(30^{\circ}) = \frac{\sqrt{3}}{2} \] Thus, the exact value of the expression is: \[ \frac{\sqrt{3}}{2} \]