u(0,t)=f'(at)+f分(-at)…(6) '(at)=f3(-at)…(5) a(0,t)=2f'(at)…(7) 4、泊松公式 将(3)两端对t求导并除以a得: 8a(]=r+a叫-乃-m-网 将3)两端对r求导得: 8[mc]-=fc+am)+g-9 (8)与(9)相加得: 8[rmv.小+arz=2f+a1o将(3)两端对t求导并除以a 得: u t f at f at 0, ( ) (6) 1 2 f at f at 1 2 (5) 1 u t f at (0, ) 2 ( ) (7) 4、泊松公式 1 2 1 ru r t f r at f r at , (8) a t 将(3)两端对r求导 得: ru r t f r at f r at , (9) 1 2 r (8)与(9)相加得: 1 1 ( , ) ( , ) 2 ( ) (10) t ru r t ru r t f r at r a