入射波在 x = 11 m 处的振动方程为
y入(x=11) = A cos2π(10t - 11/2)
= A cos[2π * 10t - 11π]
= A cos[2π * 10t - π]
反射波在 x = 11 m 处的振动方程为
y反(x=11) = A cos[2π * 10t ]
反射波的波动方程为
y反 = A cos[2π * 10t - 2π * (11-x)/2]
= A cos[2π * 10t + 2π x/2 - 2π*11/2]
= A cos[2π (10t + x/2) - π]