9. 解：ʃ(0,0)→(1,1)xy²dx+x²ydy ＝ʃ(0,0)→(1,0)xy²dx+x²ydy +ʃ(1,0)→(1,1)xy²dx+x²ydy ＝ʃ[0,1]x0²dx+ʃ[0,1]1²ydy ＝ʃ[0,1]ydy ＝(y²/2)|[0,1] ＝1/2 .
