1))当(x,y)→(1,1/2)时,
limarcsin(x^3y)/(2^x+y)
=arcsin(1^3*1/2)/(2^1+1/2)
=pai/6/(5/2)
=pai/15
2)当(x,y)→(0,0)时,
limxy/(2-√(xy+4))
=limxy*(2+√(xy+4))/[(2-√(xy+4))(2+√(xy+4))]
=limxy*(2+√(xy+4))/[(4-(xy+4)]
=limxy*(2+√(xy+4))/(-xy)
=-lim(2+√(xy+4))
=-[2+√(0+4)]
=-4