已知du(x，y)=[axy
3
+cos(x+2y)]dx+[3x
3
y
2
+bcos(x+2y)]dy，则 ( )
【正确答案】
C
【答案解析】解析：由du(x，y)=[axy
3
+cos(x+2y)]dx+[3x
2
y
2
+bcos(x+2y)]dy可知，
