曲线的性质 日 3 -3 17 2 0≤u≤1 010 ca-6 P 0≤u≤1 D i+3 曲线的性质 , 0 u 1 P P P P 0 0 1 1 2 3 0 4 3 1 2 1 [ u u 1 ] 2 1 Q (u) i 3 i 2 i 1 i 2 i                         − − − −  = + + + , 0 u 1 P P P P 0 1 1 3 2 3 1 1 Q (u) [ u 1 ] i 3 i 2 i 1 i i                     − − −  = + + +