試題詳解

7. (5%) Which functions satisfy the wave equation?
(A)u(x,t) = (x² + k²)t²
(B) u(x, t) = sin x cos kt
(C) u(x, t) = tan⁻¹(x + kt)
(D)u(x, t) = ln(x + kt)

(E) u(x, t) = e⁻ᵏᵗ sin x